NASA's Voyager 1 spacecraft has experienced a new "tsunami wave" from the sun as it sails through interstellar space. Such waves are what led scientists to the conclusion, in the fall of 2013, that Voyager had indeed left our sun's bubble, entering a new frontier.
"Normally, interstellar space is like a quiet lake," said Ed Stone of the California Institute of Technology in Pasadena, California, the mission's project scientist since 1972. "But when our sun has a burst, it sends a shock wave outward that reaches Voyager about a year later. The wave causes the plasma surrounding the spacecraft to sing."
Data from this newest tsunami wave generated by our sun confirm that Voyager is in interstellar space -- a region between the stars filled with a thin soup of charged particles, also known as plasma. The mission has not left the solar system -- it has yet to reach a final halo of comets surrounding our sun -- but it broke through the wind-blown bubble, or heliosphere, encasing our sun. Voyager is the farthest human-made probe from Earth, and the first to enter the vast sea between stars.
"All is not quiet around Voyager," said Don Gurnett of the University of Iowa, Iowa City, the principal investigator of the plasma wave instrument on Voyager, which collected the definitive evidence that Voyager 1 had left the sun's heliosphere. "We're excited to analyze these new data. So far, we can say that it confirms we are in interstellar space."
Our sun goes through periods of increased activity, where it explosively ejects material from its surface, flinging it outward. These events, called coronal mass ejections, generate shock, or pressure, waves. Three such waves have reached Voyager 1 since it entered interstellar space in 2012. The first was too small to be noticed when it occurred and was only discovered later, but the second was clearly registered by the spacecraft's cosmic ray instrument in March of 2013.
Cosmic rays are energetic charged particles that come from nearby stars in the Milky Way galaxy. The sun's shock waves push these particles around like buoys in a tsunami. Data from the cosmic ray instrument tell researchers that a shock wave from the sun has hit.
Meanwhile, another instrument on Voyager registers the shock waves, too. The plasma wave instrument can detect oscillations of the plasma electrons.
"The tsunami wave rings the plasma like a bell," said Stone. "While the plasma wave instrument lets us measure the frequency of this ringing, the cosmic ray instrument reveals what struck the bell -- the shock wave from the sun."
This ringing of the plasma bell is what led to the key evidence showing Voyager had entered interstellar space. Because denser plasma oscillates faster, the team was able to figure out the density of the plasma. In 2013, thanks to the second tsunami wave, the team acquired evidence that Voyager had been flying for more than a year through plasma that was 40 times denser than measured before -- a telltale indicator of interstellar space.
Why is it denser out there? The sun's winds blow a bubble around it, pushing out against denser matter from other stars.
Now, the team has new readings from a third wave from the sun, first registered in March of this year. These data show that the density of the plasma is similar to what was measured previously, confirming the spacecraft is in interstellar space. Thanks to our sun's rumblings, Voyager has the opportunity to listen to the singing of interstellar space -- an otherwise silent place.
Voyager 1 and its twin, Voyager 2, were launched 16 days apart in 1977. Both spacecraft flew by Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune. Voyager 2, launched before Voyager 1, is the longest continuously operated spacecraft and is expected to enter interstellar space in a few years.
JPL, a division of Caltech, built and operates the twin Voyager spacecraft. The Voyagers Interstellar Mission is a part of NASA's Heliophysics System Observatory, sponsored by the Heliophysics Division of NASA's Science Mission Directorate in Washington. NASA's Deep Space Network, managed by JPL, is an international network of antennas that supports interplanetary spacecraft missions and radio and radar astronomy observations for the exploration of the solar system and the universe. The network also supports selected Earth-orbiting missions. The spacecraft's nuclear batteries were provided by the Department of Energy.
For more information on the Voyager mission, visit: http://voyager.jpl.nasa.gov
Monday 25 August 2014
Titan's Building Blocks Might Pre-date Saturn
A combined NASA and European Space Agency (ESA)-funded study has found firm evidence that nitrogen in the atmosphere of Saturn's moon Titan originated in conditions similar to the cold birthplace of the most ancient comets from the Oort cloud. The finding rules out the possibility that Titan's building blocks formed within the warm disk of material thought to have surrounded the infant planet Saturn during its formation.
The main implication of this new research is that Titan's building blocks formed early in the solar system's history, in the cold disk of gas and dust that formed the sun. This was also the birthplace of many comets, which retain a primitive, or largely unchanged, composition today.
The research, led by Kathleen Mandt of Southwest Research Institute in San Antonio, was published this week in the Astrophysical Journal Letters. Co-authors on the study include colleagues from France's National Center for Scientific Research (CNRS) and Observatoire de Paris.
Nitrogen is the main ingredient in the atmosphere of Earth, as well as on Titan. The planet-sized moon of Saturn is frequently compared to an early version of Earth, locked in a deep freeze.
The paper suggests that information about Titan's original building blocks is still present in the icy moon's atmosphere, allowing researchers to test different ideas about how the moon might have formed. Mandt and colleagues demonstrate that a particular chemical hint as to the origin of Titan's nitrogen should be essentially the same today as when this moon formed, up to 4.6 billion years ago. That hint is the ratio of one isotope, or form, of nitrogen, called nitrogen-14, to another isotope, called nitrogen-15.
The team finds that our solar system is not old enough for this nitrogen isotope ratio to have changed significantly. This is contrary to what scientists commonly have assumed.
"When we looked closely at how this ratio could evolve with time, we found that it was impossible for it to change significantly. Titan's atmosphere contains so much nitrogen that no process can significantly modify this tracer even given more than four billion years of solar system history," Mandt said.
The small amount of change in this isotope ratio over long time periods makes it possible for researchers to compare Titan's original building blocks to other solar system objects in search of connections between them.
As planetary scientists investigate the mystery of how the solar system formed, isotope ratios are one of the most valuable types of clues they are able to collect. In planetary atmospheres and surface materials, the specific amount of one form of an element, like nitrogen, relative to another form of that same element can be a powerful diagnostic tool because it is closely tied to the conditions under which materials form.
The study also has implications for Earth. It supports the emerging view that ammonia ice from comets is not likely to be the primary source of Earth's nitrogen. In the past, researchers assumed a connection between comets, Titan and Earth, and supposed the nitrogen isotope ratio in Titan's original atmosphere was the same as that ratio is on Earth today. Measurements of the nitrogen isotope ratio at Titan by several instruments of the NASA and ESA Cassini-Huygens mission showed that this is not the case -- meaning this ratio is different on Titan and Earth -- while measurements of the ratio in comets have borne out their connection to Titan. This means the sources of Earth's and Titan's nitrogen must have been different.
Other researchers previously had shown that Earth's nitrogen isotope ratio likely has not changed significantly since our planet formed.
"Some have suggested that meteorites brought nitrogen to Earth, or that nitrogen was captured directly from the disk of gas that formed the sun. This is an interesting puzzle for future investigations," Mandt said.
Mandt and colleagues are eager to see whether their findings are supported by data from ESA's Rosetta mission, when it studies comet 67P/ Churyumov-Gerasimenko beginning later this year. If their analysis is correct, the comet should have a lower ratio of two isotopes -- in this case of hydrogen in methane ice -- than the ratio on Titan. In essence, they believe this chemical ratio on Titan is more similar to Oort cloud comets than comets born in the Kuiper Belt, which begins near the orbit of Neptune (67P/ Churyumov-Gerasimenko is a Kuiper Belt comet).
"This exciting result is a key example of Cassini science informing our knowledge of the history of solar system and how the Earth formed," said Scott Edgington, Cassini deputy project scientist at NASA's Jet Propulsion Laboratory, Pasadena, California.
The Cassini-Huygens mission is a cooperative project of NASA, ESA and the Italian Space Agency. JPL, a division of the California Institute of Technology, Pasadena, manages the mission for NASA's Science Mission Directorate in Washington.
Rosetta is an ESA mission with contributions from its member states and NASA. JPL manages the U.S. contribution of the Rosetta mission for NASA's Science Mission Directorate in Washington.
More information about Cassini is available at the following sites:
http://www.nasa.gov/cassini
http://saturn.jpl.nasa.gov
The main implication of this new research is that Titan's building blocks formed early in the solar system's history, in the cold disk of gas and dust that formed the sun. This was also the birthplace of many comets, which retain a primitive, or largely unchanged, composition today.
The research, led by Kathleen Mandt of Southwest Research Institute in San Antonio, was published this week in the Astrophysical Journal Letters. Co-authors on the study include colleagues from France's National Center for Scientific Research (CNRS) and Observatoire de Paris.
Nitrogen is the main ingredient in the atmosphere of Earth, as well as on Titan. The planet-sized moon of Saturn is frequently compared to an early version of Earth, locked in a deep freeze.
The paper suggests that information about Titan's original building blocks is still present in the icy moon's atmosphere, allowing researchers to test different ideas about how the moon might have formed. Mandt and colleagues demonstrate that a particular chemical hint as to the origin of Titan's nitrogen should be essentially the same today as when this moon formed, up to 4.6 billion years ago. That hint is the ratio of one isotope, or form, of nitrogen, called nitrogen-14, to another isotope, called nitrogen-15.
The team finds that our solar system is not old enough for this nitrogen isotope ratio to have changed significantly. This is contrary to what scientists commonly have assumed.
"When we looked closely at how this ratio could evolve with time, we found that it was impossible for it to change significantly. Titan's atmosphere contains so much nitrogen that no process can significantly modify this tracer even given more than four billion years of solar system history," Mandt said.
The small amount of change in this isotope ratio over long time periods makes it possible for researchers to compare Titan's original building blocks to other solar system objects in search of connections between them.
As planetary scientists investigate the mystery of how the solar system formed, isotope ratios are one of the most valuable types of clues they are able to collect. In planetary atmospheres and surface materials, the specific amount of one form of an element, like nitrogen, relative to another form of that same element can be a powerful diagnostic tool because it is closely tied to the conditions under which materials form.
The study also has implications for Earth. It supports the emerging view that ammonia ice from comets is not likely to be the primary source of Earth's nitrogen. In the past, researchers assumed a connection between comets, Titan and Earth, and supposed the nitrogen isotope ratio in Titan's original atmosphere was the same as that ratio is on Earth today. Measurements of the nitrogen isotope ratio at Titan by several instruments of the NASA and ESA Cassini-Huygens mission showed that this is not the case -- meaning this ratio is different on Titan and Earth -- while measurements of the ratio in comets have borne out their connection to Titan. This means the sources of Earth's and Titan's nitrogen must have been different.
Other researchers previously had shown that Earth's nitrogen isotope ratio likely has not changed significantly since our planet formed.
"Some have suggested that meteorites brought nitrogen to Earth, or that nitrogen was captured directly from the disk of gas that formed the sun. This is an interesting puzzle for future investigations," Mandt said.
Mandt and colleagues are eager to see whether their findings are supported by data from ESA's Rosetta mission, when it studies comet 67P/ Churyumov-Gerasimenko beginning later this year. If their analysis is correct, the comet should have a lower ratio of two isotopes -- in this case of hydrogen in methane ice -- than the ratio on Titan. In essence, they believe this chemical ratio on Titan is more similar to Oort cloud comets than comets born in the Kuiper Belt, which begins near the orbit of Neptune (67P/ Churyumov-Gerasimenko is a Kuiper Belt comet).
"This exciting result is a key example of Cassini science informing our knowledge of the history of solar system and how the Earth formed," said Scott Edgington, Cassini deputy project scientist at NASA's Jet Propulsion Laboratory, Pasadena, California.
The Cassini-Huygens mission is a cooperative project of NASA, ESA and the Italian Space Agency. JPL, a division of the California Institute of Technology, Pasadena, manages the mission for NASA's Science Mission Directorate in Washington.
Rosetta is an ESA mission with contributions from its member states and NASA. JPL manages the U.S. contribution of the Rosetta mission for NASA's Science Mission Directorate in Washington.
More information about Cassini is available at the following sites:
http://www.nasa.gov/cassini
http://saturn.jpl.nasa.gov
NASA's Mars Curiosity Rover Marks First Martian Year
This map shows in red the route driven by NASA's Curiosity Mars rover from the "Bradbury Landing" location where it landed in August 2012 to nearly the completion of its first Martian year. The white line shows the planned route ahead. The rover's June 18, 2014, location is marked as 663. Credit: NASA/JPL-Caltech/Univ. of Arizona/USGS
One of Curiosity's first major findings after landing on the Red Planet in August 2012 was an ancient riverbed at its landing site. Nearby, at an area known as Yellowknife Bay, the mission met its main goal of determining whether the Martian Gale Crater ever was habitable for simple life forms. The answer, a historic "yes," came from two mudstone slabs that the rover sampled with its drill. Analysis of these samples revealed the site was once a lakebed with mild water, the essential elemental ingredients for life, and a type of chemical energy source used by some microbes on Earth. If Mars had living organisms, this would have been a good home for them.
Other important findings during the first Martian year include:
-- Assessing natural radiation levels both during the flight to Mars and on the Martian surface provides guidance for designing the protection needed for human missions to Mars.
-- Measurements of heavy-versus-light variants of elements in the Martian atmosphere indicate that much of Mars' early atmosphere disappeared by processes favoring loss of lighter atoms, such as from the top of the atmosphere. Other measurements found that the atmosphere holds very little, if any, methane, a gas that can be produced biologically.
-- The first determinations of the age of a rock on Mars and how long a rock has been exposed to harmful radiation provide prospects for learning when water flowed and for assessing degradation rates of organic compounds in rocks and soils.
Curiosity paused in driving this spring to drill and collect a sample from a sandstone site called Windjana. The rover currently is carrying some of the rock-powder sample collected at the site for follow-up analysis.
"Windjana has more magnetite than previous samples we've analyzed," said David Blake, principal investigator for Curiosity's Chemistry and Mineralogy (CheMin) instrument at NASA's Ames Research Center, Moffett Field, California. "A key question is whether this magnetite is a component of the original basalt or resulted from later processes, such as would happen in water-soaked basaltic sediments. The answer is important to our understanding of habitability and the nature of the early-Mars environment."
Preliminary indications are that the rock contains a more diverse mix of clay minerals than was found in the mission's only previously drilled rocks, the mudstone targets at Yellowknife Bay. Windjana also contains an unexpectedly high amount of the mineral orthoclase, a potassium-rich feldspar that is one of the most abundant minerals in Earth's crust that had never before been definitively detected on Mars.
This finding implies that some rocks on the Gale Crater rim, from which the Windjana sandstones are thought to have been derived, may have experienced complex geological processing, such as multiple episodes of melting.
"It's too early for conclusions, but we expect the results to help us connect what we learned at Yellowknife Bay to what we'll learn at Mount Sharp," said John Grotzinger, Curiosity project scientist at the California Institute of Technology, Pasadena. "Windjana is still within an area where a river flowed. We see signs of a complex history of interaction between water and rock."
Curiosity departed Windjana in mid-May and is advancing westward. It has covered about nine-tenths of a mile (1.5 kilometers) in 23 driving days and brought the mission's odometer tally up to 4.9 miles (7.9 kilometers).
Since wheel damage prompted a slow-down in driving late in 2013, the mission team has adjusted routes and driving methods to reduce the rate of damage.
For example, the mission team revised the planned route to future destinations on the lower slope of an area called Mount Sharp, where scientists expect geological layering will yield answers about ancient environments. Before Curiosity landed, scientists anticipated that the rover would need to reach Mount Sharp to meet the goal of determining whether the ancient environment was favorable for life. They found an answer much closer to the landing site. The findings so far have raised the bar for the work ahead. At Mount Sharp, the mission team will seek evidence not only of habitability, but also of how environments evolved and what conditions favored preservation of clues to whether life existed there.
The entry gate to the mountain is a gap in a band of dunes edging the mountain's northern flank that is approximately 2.4 miles (3.9 kilometers) ahead of the rover's current location. The new path will take Curiosity across sandy patches as well as rockier ground. Terrain mapping with use of imaging from NASA's Mars Reconnaissance Orbiter enables the charting of safer, though longer, routes.
The team expects it will need to continually adapt to the threats posed by the terrain to the rover's wheels but does not expect this will be a determining factor in the length of Curiosity's operational life.
"We are getting in some long drives using what we have learned," said Jim Erickson, Curiosity project manager at NASA's Jet Propulsion Laboratory in Pasadena, California. "When you're exploring another planet, you expect surprises. The sharp, embedded rocks were a bad surprise. Yellowknife Bay was a good surprise."
JPL manages NASA's Mars Science Laboratory Project for NASA's Science Mission Directorate at the agency's headquarters in Washington, and built the project's Curiosity rover.
For more information about Curiosity, visit:
http://www.nasa.gov/msl
and
http://mars.jpl.nasa.gov/msl/
You can follow the mission on Facebook at:
http://www.facebook.com/marscuriosity
and on Twitter at:
http://www.twitter.com/marscuriosity.
Saturn Moon Titan's Underground Ocean May Be Super Salty
Video here; http://www.space.com/23947-tour-the-strange-lakes-of-saturn-s-moon-titan-video.html
The subsurface ocean inside Saturn’s largest moon, Titan, could be as salty as any body of water here on Earth, a new study reports.
Gravity data collected by NASA’s Cassini spacecraft suggest that Titan’s ocean must have an extremely high density. Salt water has a higher density than fresh water because the presence of salt adds more mass to a given amount of water.
Researchers think the ocean could be as salty as the Dead Sea of Israel and Jordan, with a high concentration of dissolved salts made of sulfur, sodium and potassium.
This is an extremely salty ocean by Earth standards," study lead author Giuseppe Mitri, from the University of Nantes in France, said in a statement. "Knowing this may change the way we view this ocean as a possible abode for present-day life, but conditions might have been very different there in the past."
The average salt concentration in Earth’s oceans is around 3.5 percent, but parts of the Dead Sea can reach 40 percent salinity.
Titan is surrounded by an ice shell, but below the surface, scientists believe there is an ocean of liquid water that could be just as salty as the Dead Sea.
Cassini collected gravity and topography data during its flybys of Titan over the past 10 years, allowing researchers to create a new model of the structure of the moon’s outer icy shell.
The new model suggests that the thickness of the icy crust varies across the moon’s surface. This means that the ocean underneath is probably in the process of freezing, too. If the ocean is freezing, it would decrease the chances that the ocean could support life, since freezing would limit the exchange of materials between the water and the surface, researchers said.
The new data could also provide some insight into Titan’s unique atmosphere, which is consistently around 5 percent methane. It is still a mystery how Titan maintains methane in its atmosphere since sunlight quickly breaks up the gas.
Scientists believe some kind of natural process must be cycling the methane into the atmosphere; from there, it falls back down to the surface as methane rain, similar to the water cycle on Earth. Since Titan’s surface is mostly frozen, researchers think any methane rising into the atmosphere must be coming from a few scattered unfrozen "hot spots."
The $3.2 billion Cassini mission launched in 1997 and arrived in orbit around Saturn in 2004. The mission also dropped a probe named Huygens onto the surface of Titan in January 2005.
The new study was published July 1 in the journal Icarus
The subsurface ocean inside Saturn’s largest moon, Titan, could be as salty as any body of water here on Earth, a new study reports.
Gravity data collected by NASA’s Cassini spacecraft suggest that Titan’s ocean must have an extremely high density. Salt water has a higher density than fresh water because the presence of salt adds more mass to a given amount of water.
Researchers think the ocean could be as salty as the Dead Sea of Israel and Jordan, with a high concentration of dissolved salts made of sulfur, sodium and potassium.
This is an extremely salty ocean by Earth standards," study lead author Giuseppe Mitri, from the University of Nantes in France, said in a statement. "Knowing this may change the way we view this ocean as a possible abode for present-day life, but conditions might have been very different there in the past."
The average salt concentration in Earth’s oceans is around 3.5 percent, but parts of the Dead Sea can reach 40 percent salinity.
Titan is surrounded by an ice shell, but below the surface, scientists believe there is an ocean of liquid water that could be just as salty as the Dead Sea.
Cassini collected gravity and topography data during its flybys of Titan over the past 10 years, allowing researchers to create a new model of the structure of the moon’s outer icy shell.
The new model suggests that the thickness of the icy crust varies across the moon’s surface. This means that the ocean underneath is probably in the process of freezing, too. If the ocean is freezing, it would decrease the chances that the ocean could support life, since freezing would limit the exchange of materials between the water and the surface, researchers said.
The new data could also provide some insight into Titan’s unique atmosphere, which is consistently around 5 percent methane. It is still a mystery how Titan maintains methane in its atmosphere since sunlight quickly breaks up the gas.
Scientists believe some kind of natural process must be cycling the methane into the atmosphere; from there, it falls back down to the surface as methane rain, similar to the water cycle on Earth. Since Titan’s surface is mostly frozen, researchers think any methane rising into the atmosphere must be coming from a few scattered unfrozen "hot spots."
The $3.2 billion Cassini mission launched in 1997 and arrived in orbit around Saturn in 2004. The mission also dropped a probe named Huygens onto the surface of Titan in January 2005.
The new study was published July 1 in the journal Icarus
Earth's Largest Solar Telescope Takes Awesome, High-Def Images of Sun
See article; http://www.space.com/26343-largest-solar-telescope-sun-video.html?cmpid=557678
'Magic Island' Possibly Seen in Seas of Saturn's Huge Moon Titan
http://www.space.com/26326-peculiar-island-appears-on-saturn-moon-before-and-after-spacecraft-shots-video.html
Scientists may have spotted waves in the seas of Saturn's moon Titan, as depicted in this image.
A mysteriously bright anomaly winked in and out of existence on the seas of Saturn's largest moon, Titan — potentially the first time waves, bubbles or some other unknown features have been seen there, scientists say.
Scientists usually call this spot a "transient feature," but the researchers have playfully dubbed it "Magic Island." Titan, the largest of Saturn's 62 known moons, is 50 percent wider than Earth's moon and 80 percent more massive. You can watch a video about the "Magic Island" on Space.com.
"What I think is really special about Titan is that it has liquid methane and ethane lakes and seas, making it the only other world in the solar system that has stable liquids on its surfaces," lead study author Jason Hofgartner, a planetary scientist at Cornell University,told Space.com. "It not only has lakes and seas, but also rivers and even rain. It has what we call a hydrological cycle, and we can study it as an analog to Earth's hydrological cycle — and it's the only other place we know of where we can do that." [Titan, Saturn's Largest Moon.
Using radar aboard NASA's Cassini spacecraft, Hofgartner and his colleagues peered through Titan's thick, hazy atmosphere to analyze Ligeia Mare, the second-largest sea on Titan. Ligeia Mare is named after one of the Sirens from Greek mythology, and is about 48,650 square miles (126,000 square kilometers) in size, making it larger than North America's Lake Superior.
After the Cassini probe sent data to researchers in July 2013, the researchers flipped between older Titan photos and the newly processed images, to look for any hints of change. This is a long-standing method used to discover asteroids, comets and other worlds.
"With flipping, the human eye is pretty good at detecting change," Hofgartner said in a statement.
Prior to the July 2013 data, the region the scientists analyzed was completely devoid of features, including waves
Titan's seas and lakes are usually pretty dark, Hofgartner said. "The way the radar system works is by transmitting radio beams at Titan, which scatter off its surface and back at the radar system. The seas are normally so flat; all the radar energy is scattered away and doesn't come back to the spacecraft, so the seas appear perfectly dark," he explained.
However, in July 2013, Cassini detected features that are essentially as bright as the surrounding terrain. The anomaly disappeared after subsequent observations.
"These are not stagnant seas — they are not unchanging and constant in state," Hofgartner said. "They are active and do change."
It remains uncertain "precisely what caused this 'magic island' to appear, but we'd like to study it further," Hofgartner said in a statement. He and his colleagues detailed their findings June 22 in the journal Nature Geoscience.
The bright anomaly occupies an area of about 6.2 by 12.4 miles (10 by 20 km), Hofgartner said.
"We don't think this is one large feature, but it is probably broken up into a few features — some no bigger than about 1 km by 1 km [0.6 by 0.6 miles]," Hofgartner said. "However, we do think at least one of them is bigger than 1 km by 1 km."
The researchers do not think this anomaly is an alien creature or spacecraft. Rather, now that Titan's northern hemisphere is entering its summer season, "it's probably receiving enough solar energy to drive winds and power other phenomena," Hofgartner said.
The seas are normally very smooth on Titan, "with features no taller than 1 to 3 millimeters (.04 to 0.12 inches), making them smoother than any natural surface on Earth," Hofgartner said. "This is because the winds on Titan have likely not been strong enough to create waves. Now, however, the winds might be getting stronger, and we might be seeing waves," he added.
Another possibility is that the bright anomaly could represent gases pushing up from the seafloor and rising as bubbles. It could also represent solids becoming buoyant with the onset of warmer temperatures and floating on the surface, or solids that are neither sunken nor floating, but rather suspended in the sea like silt in a delta on Earth. "As summer comes on Titan, we hope to learn more about the seas there," Hofgartner said.
Discovering more about how the seas of Titan work "can help us with future plans to explore Titan," Hofgartner said. "One plan is to put a boat or raft on Titan's seas to study it in more detail, and understanding what processes are happening there now can tell us what instrumentation to bring and also how to improve the safety of the craft as well," he said
A mysteriously bright anomaly winked in and out of existence on the seas of Saturn's largest moon, Titan — potentially the first time waves, bubbles or some other unknown features have been seen there, scientists say.
Scientists usually call this spot a "transient feature," but the researchers have playfully dubbed it "Magic Island." Titan, the largest of Saturn's 62 known moons, is 50 percent wider than Earth's moon and 80 percent more massive. You can watch a video about the "Magic Island" on Space.com.
"What I think is really special about Titan is that it has liquid methane and ethane lakes and seas, making it the only other world in the solar system that has stable liquids on its surfaces," lead study author Jason Hofgartner, a planetary scientist at Cornell University,told Space.com. "It not only has lakes and seas, but also rivers and even rain. It has what we call a hydrological cycle, and we can study it as an analog to Earth's hydrological cycle — and it's the only other place we know of where we can do that." [Titan, Saturn's Largest Moon.
Using radar aboard NASA's Cassini spacecraft, Hofgartner and his colleagues peered through Titan's thick, hazy atmosphere to analyze Ligeia Mare, the second-largest sea on Titan. Ligeia Mare is named after one of the Sirens from Greek mythology, and is about 48,650 square miles (126,000 square kilometers) in size, making it larger than North America's Lake Superior.
After the Cassini probe sent data to researchers in July 2013, the researchers flipped between older Titan photos and the newly processed images, to look for any hints of change. This is a long-standing method used to discover asteroids, comets and other worlds.
"With flipping, the human eye is pretty good at detecting change," Hofgartner said in a statement.
Prior to the July 2013 data, the region the scientists analyzed was completely devoid of features, including waves
Titan's seas and lakes are usually pretty dark, Hofgartner said. "The way the radar system works is by transmitting radio beams at Titan, which scatter off its surface and back at the radar system. The seas are normally so flat; all the radar energy is scattered away and doesn't come back to the spacecraft, so the seas appear perfectly dark," he explained.
However, in July 2013, Cassini detected features that are essentially as bright as the surrounding terrain. The anomaly disappeared after subsequent observations.
"These are not stagnant seas — they are not unchanging and constant in state," Hofgartner said. "They are active and do change."
It remains uncertain "precisely what caused this 'magic island' to appear, but we'd like to study it further," Hofgartner said in a statement. He and his colleagues detailed their findings June 22 in the journal Nature Geoscience.
The bright anomaly occupies an area of about 6.2 by 12.4 miles (10 by 20 km), Hofgartner said.
"We don't think this is one large feature, but it is probably broken up into a few features — some no bigger than about 1 km by 1 km [0.6 by 0.6 miles]," Hofgartner said. "However, we do think at least one of them is bigger than 1 km by 1 km."
The researchers do not think this anomaly is an alien creature or spacecraft. Rather, now that Titan's northern hemisphere is entering its summer season, "it's probably receiving enough solar energy to drive winds and power other phenomena," Hofgartner said.
The seas are normally very smooth on Titan, "with features no taller than 1 to 3 millimeters (.04 to 0.12 inches), making them smoother than any natural surface on Earth," Hofgartner said. "This is because the winds on Titan have likely not been strong enough to create waves. Now, however, the winds might be getting stronger, and we might be seeing waves," he added.
Another possibility is that the bright anomaly could represent gases pushing up from the seafloor and rising as bubbles. It could also represent solids becoming buoyant with the onset of warmer temperatures and floating on the surface, or solids that are neither sunken nor floating, but rather suspended in the sea like silt in a delta on Earth. "As summer comes on Titan, we hope to learn more about the seas there," Hofgartner said.
Discovering more about how the seas of Titan work "can help us with future plans to explore Titan," Hofgartner said. "One plan is to put a boat or raft on Titan's seas to study it in more detail, and understanding what processes are happening there now can tell us what instrumentation to bring and also how to improve the safety of the craft as well," he said
Higgs Boson Confirms Reigning Physics Model Yet Again
For a subatomic particle that remained hidden for nearly 50 years, the Higgs boson is turning out to be remarkably well behaved.
Yet more evidence from the world's largest particle accelerator, the Large Hadron Collider (LHC) in Switzerland, confirms that the Higgs boson particle, thought to explain why other particles have mass, acts just as predicted by the Standard Model, the dominant physics theory that describes the menagerie of subatomic particles that make up the universe.
"This is exactly what we have expected from the Standard Model," said Markus Klute, a physicist at the Massachusetts Institute of Technology and one of the researchers involved in the Higgs search.
The new results show that the Higgs boson decays into subatomic particles that carry matter called fermions — in particular, it decays into a heavier brother particle of the electron called a tau lepton, Klute said. This decay has been predicted by the Standard Model. Even so, the findings are a bit of a disappointment for physicists who were hoping for hints of completely new physics.
On July 4, 2012, scientists at the LHC announced they had found the Higgs boson, an elusive particle first proposed 50 years ago by English physicist Peter Higgs. In Higgs' conception, in the blink after the Big Bang, an energy field, now dubbed the Higgs field, emerged that imparts mass to the subatomic particles that trawl through it. Particles that are "stickier" and slow down more while traversing the field become heavier.
Because subatomic particles are either matter carriers called fermions, such as electrons and protons, or force-carrying particles called bosons, such as photons and gluons, the existence of the Higgs field implied an associated force-carrying particle, called the Higgs boson, which is like a ripple in that field, Klute said.
The 2012 discovery left little doubt that the Higgs boson exists, and Higgs and his colleague, François Englert, won the Nobel Prize for the theory in 2013. But there were still many unanswered questions. Is there one Higgs boson or multiple? If there are multiple, what are their masses? And just how do these different-flavored Higgs behave?
To answer those questions, physicists still had to pore over tons of data from the LHC, which accelerates protons to just below the speed of light, then smashes them together, creating a shower of subatomic particles.
Of the billions of collisions produced by the LHC every second, just a few hundred had the signature energy levels associated with the Higgs boson, Klute said.
When the LHC collaborators analyzed those Higgs events, they found about 6 percent of the elusive particles decayed into tau leptons, Klute told Live Science. And though not unexpected, the new results show no hint of additional Higgs bosons that would lend credence to alternate theories such as supersymmetry, which predicts that every particle currently known has a "superpartner" with slightly different properties.
The idea of the Higgs decaying to tau leptons was somewhat tacked onto the Standard Model after its creation, yet this "ad hoc addition to the Standard model turns out to be how nature does it," Klute said.
But there are still a few pieces left to complete the picture predicted by the Standard Model, said Nitesh Soni, a particle physicist at the University of Adelaide in Australia, who works on a different experiment at the LHC that focuses on similar physics questions.
"The Higgs is predicted to decay into some other particles too, but those have relatively smaller decay rates and higher background" noise, making it too difficult to detect those particles from the current dataset, Soni said.
Though the Standard Model has been stunningly successful at predicting behavior in the subatomic realm, there has to be more to the laws of nature, Klute said.
For instance, the Standard Model can't explain dark matter or the existence of gravity. So the lack of evidence for something new is a little disappointing, Klute said.
"My hope was that we would already find some new physics," Klute said.
But he's not giving up hope yet. The hunt for new particles will continue once the LHC is turned on again at much higher energies in 2015, Klute said.
The new analysis of the LHC data was published yesterday (June 22) in the journal Nature Physics.
Editor's Note: This story was updated to add information on Nitesh Soni's research.
Yet more evidence from the world's largest particle accelerator, the Large Hadron Collider (LHC) in Switzerland, confirms that the Higgs boson particle, thought to explain why other particles have mass, acts just as predicted by the Standard Model, the dominant physics theory that describes the menagerie of subatomic particles that make up the universe.
"This is exactly what we have expected from the Standard Model," said Markus Klute, a physicist at the Massachusetts Institute of Technology and one of the researchers involved in the Higgs search.
The new results show that the Higgs boson decays into subatomic particles that carry matter called fermions — in particular, it decays into a heavier brother particle of the electron called a tau lepton, Klute said. This decay has been predicted by the Standard Model. Even so, the findings are a bit of a disappointment for physicists who were hoping for hints of completely new physics.
On July 4, 2012, scientists at the LHC announced they had found the Higgs boson, an elusive particle first proposed 50 years ago by English physicist Peter Higgs. In Higgs' conception, in the blink after the Big Bang, an energy field, now dubbed the Higgs field, emerged that imparts mass to the subatomic particles that trawl through it. Particles that are "stickier" and slow down more while traversing the field become heavier.
Because subatomic particles are either matter carriers called fermions, such as electrons and protons, or force-carrying particles called bosons, such as photons and gluons, the existence of the Higgs field implied an associated force-carrying particle, called the Higgs boson, which is like a ripple in that field, Klute said.
The 2012 discovery left little doubt that the Higgs boson exists, and Higgs and his colleague, François Englert, won the Nobel Prize for the theory in 2013. But there were still many unanswered questions. Is there one Higgs boson or multiple? If there are multiple, what are their masses? And just how do these different-flavored Higgs behave?
To answer those questions, physicists still had to pore over tons of data from the LHC, which accelerates protons to just below the speed of light, then smashes them together, creating a shower of subatomic particles.
Of the billions of collisions produced by the LHC every second, just a few hundred had the signature energy levels associated with the Higgs boson, Klute said.
When the LHC collaborators analyzed those Higgs events, they found about 6 percent of the elusive particles decayed into tau leptons, Klute told Live Science. And though not unexpected, the new results show no hint of additional Higgs bosons that would lend credence to alternate theories such as supersymmetry, which predicts that every particle currently known has a "superpartner" with slightly different properties.
The idea of the Higgs decaying to tau leptons was somewhat tacked onto the Standard Model after its creation, yet this "ad hoc addition to the Standard model turns out to be how nature does it," Klute said.
But there are still a few pieces left to complete the picture predicted by the Standard Model, said Nitesh Soni, a particle physicist at the University of Adelaide in Australia, who works on a different experiment at the LHC that focuses on similar physics questions.
"The Higgs is predicted to decay into some other particles too, but those have relatively smaller decay rates and higher background" noise, making it too difficult to detect those particles from the current dataset, Soni said.
Though the Standard Model has been stunningly successful at predicting behavior in the subatomic realm, there has to be more to the laws of nature, Klute said.
For instance, the Standard Model can't explain dark matter or the existence of gravity. So the lack of evidence for something new is a little disappointing, Klute said.
"My hope was that we would already find some new physics," Klute said.
But he's not giving up hope yet. The hunt for new particles will continue once the LHC is turned on again at much higher energies in 2015, Klute said.
The new analysis of the LHC data was published yesterday (June 22) in the journal Nature Physics.
Editor's Note: This story was updated to add information on Nitesh Soni's research.
Herschel Sees Budding Stars and a Giant, Strange Ring
The Herschel Space Observatory has uncovered a weird ring of dusty material while obtaining one of the sharpest scans to date of a huge cloud of gas and dust, called NGC 7538. The observations have revealed numerous clumps of material, a baker's dozen of which may evolve into the most powerful kinds of stars in the universe. Herschel is a European Space Agency mission with important NASA contributions.
"We have looked at NGC 7538 with Herschel and identified 13 massive, dense clumps where colossal stars could form in the future," said paper lead author Cassandra Fallscheer, a visiting assistant professor of astronomy at Whitman College in Walla Walla, Washington, and lead author of the paper published in The Astrophysical Journal. "In addition, we have found a gigantic ring structure and the weird thing is, we're not at all sure what created it."
NGC 7538 is relatively nearby, at a distance of about 8,800 light-years and located in the constellation Cepheus. The cloud, which has a mass on the order of 400,000 suns, is undergoing an intense bout of star formation. Astronomers study stellar nurseries such as NGC 7538 to better learn how stars come into being. Finding the mysterious ring, in this case, came as an unexpected bonus.
The cool, dusty ring has an oval shape, with its long axis spanning about 35 light-years and its short axis about 25 light-years. Fallscheer and her colleagues estimate that the ring possesses the mass of 500 suns. Additional data from the James Clerk Maxwell Telescope, located at the Mauna Kea Observatory in Hawaii, further helped characterize the odd ovoid. Astronomers often see ring and bubble-like structures in cosmic dust clouds. The strong winds cast out by the most massive stars, called O-type stars, can generate these expanding puffs, as can their explosive deaths as supernovas. But no energetic source or remnant of a deceased O-type star, such as a neutron star, is apparent within the center of this ring. It is possible that a big star blew the bubble and, because stars are all in motion, subsequently left the scene, escaping detection.
The observations were taken as part of the Herschel OB Young Stellar objects (HOBYS) Key Programme. The "OB" refers to the two most massive kinds of stars, O-type and B-type. These bright blue, superhot, short-lived stars end up exploding as supernovas, leaving behind either incredibly dense neutron stars or even denser black holes.
Stars of this caliber form from gassy, dusty clumps with initial masses dozens of times greater than the sun's; the 13 clumps spotted in NGC 7358, some of which lie along the edge of the mystery ring, all are more than 40 times more massive than the sun. The clumps gravitationally collapse in on themselves, growing denser and hotter in their cores until nuclear fusion ignites and a star is born. For now, early in the star-formation process, the clumps remain quite cold, just a few tens of degrees above absolute zero. At these temperatures, the clumps emit the bulk of their radiation in the low-energy, submillimeter and infrared light that Herschel was specifically designed to detect.
As astronomers continue probing these budding O-type giants in NGC 7358, the follow-up observations with other telescopes should also help in solving the puzzle of the humongous, dusty ring. "Further research to determine the mechanism responsible for creating the ring structure is necessary," said Fallscheer.
Herschel is a European Space Agency mission, with science instruments provided by consortia of European institutes and with important participation by NASA. While the observatory stopped making science observations in April 2013, after running out of liquid coolant as expected, scientists continue to analyze its data. NASA's Herschel Project Office is based at the Jet Propulsion Laboratory in Pasadena, California. JPL contributed mission-enabling technology for two of Herschel's three science instruments. The NASA Herschel Science Center, part of the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena, supports the U.S. astronomical community.
More information is online at:
http://www.herschel.caltech.edu
http://www.nasa.gov/herschel
http://www.esa.int/SPECIALS/Herschel
New Suspect Identified in Supernova Explosion
New results from NASA's Spitzer Space Telescope have revealed a rare example of Type Ia explosion, in which a dead star "fed" off an aging star like a cosmic zombie, triggering a blast. The results help researchers piece together how these powerful and diverse events occur.
"It's kind of like being a detective," said Brian Williams of NASA's Goddard Space Flight Center in Greenbelt, Maryland, lead author of a study submitted to the Astrophysical Journal. "We look for clues in the remains to try to figure out what happened, even though we weren't there to see it."
Supernovas are essential factories in the cosmos, churning out heavy metals, including the iron contained in our blood. Type Ia supernovas tend to blow up in consistent ways, and thus have been used for decades to help scientists study the size and expansion of our universe. Researchers say that these events occur when white dwarfs -- the burnt-out corpses of stars like our sun -- explode.
Evidence has been mounting over the past 10 years that the explosions are triggered when two orbiting white dwarfs collide -- with one notable exception. Kepler's supernova, named after the astronomer Johannes Kepler, who was among those who witnessed it in 1604, is thought to have been preceded by just one white dwarf and an elderly, companion star called a red giant. Scientists know this because the remnant sits in a pool of gas and dust shed by the aging star.
Spitzer's new observations now find a second case of a supernova remnant resembling Kepler's. Called N103B, the roughly 1,000 year-old supernova remnant lies 160,000 light-years away in the Large Magellanic Cloud, a small galaxy near our Milky Way.
"It's like Kepler's older cousin," said Williams. He explained that N103B, though somewhat older than Kepler's supernova remnant, also lies in a cloud of gas and dust thought to have been blown off by an older companion star. "The region around the remnant is extraordinarily dense," he said. Unlike Kepler's supernova remnant, no historical sightings of the explosion that created N103B are recorded.
Both the Kepler and N103B explosions are thought to have unfolded as follows: an aging star orbits its companion -- a white dwarf. As the aging star molts, which is typical for older stars, some of the shed material falls onto the white dwarf. This causes the white dwarf to build up in mass, become unstable and explode.
According to the researchers, this scenario may be rare. While the pairing of white dwarfs and red giants was thought to underlie virtually all Type Ia supernovas as recently as a decade ago, scientists now think that collisions between two white dwarfs are the most common cause. The new Spitzer research highlights the complexity of these tremendous explosions and the variety of their triggers. The case of what makes a dead star rupture is still very much an unsolved mystery.
NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA.
For more information about Spitzer, visit: http://spitzer.caltech.edu
http://www.nasa.gov/spitzer
Astronomers Confounded By Massive Rocky World
Astronomers have discovered a rocky planet that weighs 17 times as much as Earth and is more than twice as large in size. This discovery has planet formation theorists challenged to explain how such a world could have formed.
"We were very surprised when we realized what we had found," said astronomer Xavier Dumusque of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, who led the analysis using data originally collected by NASA's Kepler space telescope.
Kepler-10c, as the planet had been named, had a previously measured size of 2.3 times larger than Earth, but its mass was not known until now. The team used the HARPS-North instrument on the Telescopio Nazionale Galileo in the Canary Islands to conduct follow-up observations to obtain a mass measurement of the rocky behemoth.
It was thought worlds such as this could not possibly exist. The enormous gravitational force of such a massive body would accrete a gas envelope during formation, ballooning the planet to a gas giant the size of Neptune or even Jupiter. However, this planet is thought to be solid, composed primarily of rock.
"Just when you think you've got it all figured out, nature gives you a huge surprise -- in this case, literally," said Natalie Batalha, Kepler mission scientist at NASA's Ames Research Center in Moffett Field, California. "Isn't science marvelous?"
Kepler-10c orbits a sun-like star every 45 days, making it too hot to sustain life as we know it. It is located about 560 light-years from Earth in the constellation Draco. The system also hosts Kepler-10b, the first rocky planet discovered in the Kepler data.
The finding was presented today at a meeting of the American Astronomical Society in Boston. Read more about the discovery in the Harvard-Smithsonian Center for Astrophysics news release.
NASA's Ames Research Center manages Kepler's ground system development, mission operations and science data analysis. NASA's Jet Propulsion Laboratory, Pasadena, California, managed the Kepler mission's development.
Ball Aerospace and Technologies Corp. in Boulder, Colorado, developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.
The Space Telescope Science Institute in Baltimore archives, hosts and distributes Kepler science data. Kepler is NASA's 10th Discovery Mission and is funded by NASA's Science Mission Directorate at the agency's headquarters in Washington.
For more information about the Kepler mission, visit:
http://www.nasa.gov/kepler
For more information about exoplanets and NASA's planet-finding program, visit:
http://planetquest.jpl.nasa.gov
"We were very surprised when we realized what we had found," said astronomer Xavier Dumusque of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, who led the analysis using data originally collected by NASA's Kepler space telescope.
Kepler-10c, as the planet had been named, had a previously measured size of 2.3 times larger than Earth, but its mass was not known until now. The team used the HARPS-North instrument on the Telescopio Nazionale Galileo in the Canary Islands to conduct follow-up observations to obtain a mass measurement of the rocky behemoth.
It was thought worlds such as this could not possibly exist. The enormous gravitational force of such a massive body would accrete a gas envelope during formation, ballooning the planet to a gas giant the size of Neptune or even Jupiter. However, this planet is thought to be solid, composed primarily of rock.
"Just when you think you've got it all figured out, nature gives you a huge surprise -- in this case, literally," said Natalie Batalha, Kepler mission scientist at NASA's Ames Research Center in Moffett Field, California. "Isn't science marvelous?"
Kepler-10c orbits a sun-like star every 45 days, making it too hot to sustain life as we know it. It is located about 560 light-years from Earth in the constellation Draco. The system also hosts Kepler-10b, the first rocky planet discovered in the Kepler data.
The finding was presented today at a meeting of the American Astronomical Society in Boston. Read more about the discovery in the Harvard-Smithsonian Center for Astrophysics news release.
NASA's Ames Research Center manages Kepler's ground system development, mission operations and science data analysis. NASA's Jet Propulsion Laboratory, Pasadena, California, managed the Kepler mission's development.
Ball Aerospace and Technologies Corp. in Boulder, Colorado, developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.
The Space Telescope Science Institute in Baltimore archives, hosts and distributes Kepler science data. Kepler is NASA's 10th Discovery Mission and is funded by NASA's Science Mission Directorate at the agency's headquarters in Washington.
For more information about the Kepler mission, visit:
http://www.nasa.gov/kepler
For more information about exoplanets and NASA's planet-finding program, visit:
http://planetquest.jpl.nasa.gov
Thursday 21 August 2014
Until now, all of the quarry's fossil meteorites were L-chondrites. Schmitz, who has led the chondrite cataloging, admitted the rock hunt had become "quite boring."
But the rare find has not only revitalized interest in the quarry, it has also brought together the world's top meteorite experts for a global hunt through geologic time. Thanks to Schmitz's careful detective work on meteorites, scientists now know that each kind of meteorite leaves behind a unique calling card: tough minerals called spinels. Even if meteorites weather away, their spinels linger for hundreds of million of years in Earth rocks. Schmitz and his cohorts think they can pin down how many meteorites rained down on Earth in the past 2.5 billion years, as well as what kind fell, by extracting extraterrestrial spinels from sedimentary rocks. Their work may confirm suspicions that recent meteorite falls represent a mere fraction of the rocks drifting in space.
"I think our new finding adds to the understanding that the meteorites that come down on Earth today may not be entirely representative of what is out there," Schmitz said. "One thing our study shows is that we maybe don't know as much as we think we know about the solar system."
The limestone quarry preserves the remnants of a cosmic cataclysm that took place 470 million years ago, during the Ordovician Period. Scientists think there was an enormous crash between two large bodies out in the asteroid belt. The crash blew apart two asteroids, or an asteroid and comet, slinging dust and debris toward Earth. One of the impactors was the source of all L-chondrite meteorites. But no one has ever found a piece of the rock that hit the L-chondrite parent, until now.
The Swedish meteorite's exposure age — the length of time it sailed through space — is the key to placing the fossil space rock at the scene of the crash. The meteorite zipped from the asteroid belt to Earth in just 1 million years. That's the same remarkably young exposure age as the L-chondrites recovered from the Thorsberg quarry, suggesting the rocks sprayed Earth in the same wave of space debris.
Meteorite expert Tim Swindle, who was not involved in the study, praised the team's careful analysis and said it was unlikely that any other meteorite but an Ordovician fragment would have such a short exposure age. "Very, very few modern meteorites have exposure ages that low," said Swindle, a professor at the University of Arizona in Tucson. "Typically, it takes things longer to get here from the asteroid belt," he said. "It's a telling argument."
Cassini 10 Years at Saturn Top 10 Discoveries
- The Huygens probe makes first landing on a moon in the outer solar system (Titan)
- Discovery of active, icy plumes on the Saturnian moon Enceladus
- Saturn’s rings revealed as active and dynamic -- a laboratory for how planets form
- Titan revealed as Earth-like world with rain, rivers, lakes and seas
- Studies of the great northern storm of 2010-2011
- Radio-wave patterns shown not to be tied to Saturn’s interior rotation as previously thought
- Vertical structures in the rings imaged for the first time
- Study of prebiotic chemistry on Titan
- Mystery of the dual bright-dark surface of Iapetus solved
- First complete view of the north polar hexagon and discovery of giant hurricanes at both of Saturn’s poles
Sunsets on Titan Reveal the Complexity of Hazy Exoplanets
Scientists working with data from NASA's Cassini mission have developed a new way to understand the atmospheres of exoplanets by using Saturn's smog-enshrouded moon Titan as a stand-in. The new technique shows the dramatic influence that hazy skies could have on our ability to learn about these alien worlds orbiting distant stars.
The work was performed by a team of researchers led by Tyler Robinson, a NASA Postdoctoral Research Fellow at NASA's Ames Research Center in Moffett Field, California. The findings were published May 26 in the Proceedings of the National Academy of Sciences.
"It turns out there's a lot you can learn from looking at a sunset," Robinson said.
Light from sunsets, stars and planets can be separated into its component colors to create spectra, as prisms do with sunlight, in order to obtain hidden information. Despite the staggering distances to other planetary systems, in recent years researchers have begun to develop techniques for collecting spectra of exoplanets. When one of these worlds transits, or passes in front of its host star as seen from Earth, some of the star's light travels through the exoplanet's atmosphere, where it is changed in subtle, but measurable, ways. This process imprints information about the planet that can be collected by telescopes. The resulting spectra are a record of that imprint.
Spectra enable scientists to tease out details about what exoplanets are like, such as aspects of the temperature, composition and structure of their atmospheres.
Robinson and his colleagues exploited a similarity between exoplanet transits and sunsets witnessed by the Cassini spacecraft at Titan. These observations, called solar occultations, effectively allowed the scientists to observe Titan as a transiting exoplanet without having to leave the solar system. In the process, Titan's sunsets revealed just how dramatic the effects of hazes can be.
Multiple worlds in our own solar system, including Titan, are blanketed by clouds and high-altitude hazes. Scientists expect that many exoplanets would be similarly obscured. Clouds and hazes create a variety of complicated effects that researchers must work to disentangle from the signature of these alien atmospheres, and thus present a major obstacle for understanding transit observations. Due to the complexity and computing power required to address hazes, models used to understand exoplanet spectra usually simplify their effects.
"Previously, it was unclear exactly how hazes were affecting observations of transiting exoplanets," said Robinson. "So we turned to Titan, a hazy world in our own solar system that has been extensively studied by Cassini."
The team used four observations of Titan made between 2006 and 2011 by Cassini's visual and infrared mapping spectrometer instrument. Their analysis provided results that include the complex effects due to hazes, which can now be compared to exoplanet models and observations.
With Titan as their example, Robinson and colleagues found that hazes high above some transiting exoplanets might strictly limit what their spectra can reveal to planet transit observers. The observations might be able to glean information only from a planet's upper atmosphere. On Titan, that corresponds to about 90 to 190 miles (150 to 300 kilometers) above the moon's surface, high above the bulk of its dense and complex atmosphere.
An additional finding from the study is that Titan's hazes more strongly affect shorter wavelengths, or bluer, colors of light. Studies of exoplanet spectra have commonly assumed that hazes would affect all colors of light in similar ways. Studying sunsets through Titan's hazes has revealed that this is not the case.
"People had dreamed up rules for how planets would behave when seen in transit, but Titan didn't get the memo," said Mark Marley, a co-author of the study at NASA Ames. "It looks nothing like some of the previous suggestions, and it's because of the haze."
The team's technique applies equally well to similar observations taken from orbit around any world, not just Titan. This means that researchers could study the atmospheres of planets like Mars and Saturn in the context of exoplanet atmospheres as well.
"It's rewarding to see that Cassini's study of the solar system is helping us to better understand other solar systems as well," said Curt Niebur, Cassini program scientist at NASA Headquarters in Washington.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology, Pasadena, manages the mission for NASA's Science Mission Directorate in Washington. The VIMS team is based at the University of Arizona in Tucson.
More information about Cassini is available at the following sites:
http://www.nasa.gov/cassini
http://saturn.jpl.nasa.gov
The work was performed by a team of researchers led by Tyler Robinson, a NASA Postdoctoral Research Fellow at NASA's Ames Research Center in Moffett Field, California. The findings were published May 26 in the Proceedings of the National Academy of Sciences.
"It turns out there's a lot you can learn from looking at a sunset," Robinson said.
Light from sunsets, stars and planets can be separated into its component colors to create spectra, as prisms do with sunlight, in order to obtain hidden information. Despite the staggering distances to other planetary systems, in recent years researchers have begun to develop techniques for collecting spectra of exoplanets. When one of these worlds transits, or passes in front of its host star as seen from Earth, some of the star's light travels through the exoplanet's atmosphere, where it is changed in subtle, but measurable, ways. This process imprints information about the planet that can be collected by telescopes. The resulting spectra are a record of that imprint.
Spectra enable scientists to tease out details about what exoplanets are like, such as aspects of the temperature, composition and structure of their atmospheres.
Robinson and his colleagues exploited a similarity between exoplanet transits and sunsets witnessed by the Cassini spacecraft at Titan. These observations, called solar occultations, effectively allowed the scientists to observe Titan as a transiting exoplanet without having to leave the solar system. In the process, Titan's sunsets revealed just how dramatic the effects of hazes can be.
Multiple worlds in our own solar system, including Titan, are blanketed by clouds and high-altitude hazes. Scientists expect that many exoplanets would be similarly obscured. Clouds and hazes create a variety of complicated effects that researchers must work to disentangle from the signature of these alien atmospheres, and thus present a major obstacle for understanding transit observations. Due to the complexity and computing power required to address hazes, models used to understand exoplanet spectra usually simplify their effects.
"Previously, it was unclear exactly how hazes were affecting observations of transiting exoplanets," said Robinson. "So we turned to Titan, a hazy world in our own solar system that has been extensively studied by Cassini."
The team used four observations of Titan made between 2006 and 2011 by Cassini's visual and infrared mapping spectrometer instrument. Their analysis provided results that include the complex effects due to hazes, which can now be compared to exoplanet models and observations.
With Titan as their example, Robinson and colleagues found that hazes high above some transiting exoplanets might strictly limit what their spectra can reveal to planet transit observers. The observations might be able to glean information only from a planet's upper atmosphere. On Titan, that corresponds to about 90 to 190 miles (150 to 300 kilometers) above the moon's surface, high above the bulk of its dense and complex atmosphere.
An additional finding from the study is that Titan's hazes more strongly affect shorter wavelengths, or bluer, colors of light. Studies of exoplanet spectra have commonly assumed that hazes would affect all colors of light in similar ways. Studying sunsets through Titan's hazes has revealed that this is not the case.
"People had dreamed up rules for how planets would behave when seen in transit, but Titan didn't get the memo," said Mark Marley, a co-author of the study at NASA Ames. "It looks nothing like some of the previous suggestions, and it's because of the haze."
The team's technique applies equally well to similar observations taken from orbit around any world, not just Titan. This means that researchers could study the atmospheres of planets like Mars and Saturn in the context of exoplanet atmospheres as well.
"It's rewarding to see that Cassini's study of the solar system is helping us to better understand other solar systems as well," said Curt Niebur, Cassini program scientist at NASA Headquarters in Washington.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology, Pasadena, manages the mission for NASA's Science Mission Directorate in Washington. The VIMS team is based at the University of Arizona in Tucson.
More information about Cassini is available at the following sites:
http://www.nasa.gov/cassini
http://saturn.jpl.nasa.gov
NASA's WISE Findings Poke Hole in Black Hole 'Doughnut' Theory
A survey of more than 170,000 supermassive black holes, using NASA's Wide-field Infrared Survey Explorer (WISE), has astronomers reexamining a decades-old theory about the varying appearances of these interstellar objects.
The unified theory of active, supermassive black holes, first developed in the late 1970s, was created to explain why black holes, though similar in nature, can look completely different. Some appear to be shrouded in dust, while others are exposed and easy to see.
The unified model answers this question by proposing that every black hole is surrounded by a dusty, doughnut-shaped structure called a torus. Depending on how these "doughnuts" are oriented in space, the black holes will take on various appearances. For example, if the doughnut is positioned so that we see it edge-on, the black hole is hidden from view. If the doughnut is observed from above or below, face-on, the black hole is clearly visible.
However, the new WISE results do not corroborate this theory. The researchers found evidence that something other than a doughnut structure may, in some circumstances, determine whether a black hole is visible or hidden. The team has not yet determined what this may be, but the results suggest the unified, or doughnut, model does not have all the answers.
"Our finding revealed a new feature about active black holes we never knew before, yet the details remain a mystery," said Lin Yan of NASA's Infrared Processing and Analysis Center (IPAC), based at the California Institute of Technology in Pasadena. "We hope our work will inspire future studies to better understand these fascinating objects."
Yan is the second author of the research accepted for publication in the Astrophysical Journal. The lead author is a post-doctoral researcher, Emilio Donoso, who worked with Yan at IPAC and has since moved to the Instituto de Ciencias Astronómicas, de la Tierra y del Espacio in Argentina. The research also was co-authored by Daniel Stern at NASA's Jet Propulsion Laboratory in Pasadena, California, and Roberto Assef of Universidad Diego Portales in Chile and formerly of JPL.
Every galaxy has a massive black hole at its heart. The new study focuses on the "feeding" ones, called active, supermassive black holes, or active galactic nuclei. These black holes gorge on surrounding gas material that fuels their growth.
With the aid of computers, scientists were able to pick out more than 170,000 active supermassive black holes from the WISE data. They then measured the clustering of the galaxies containing both hidden and exposed black holes -- the degree to which the objects clump together across the sky.
If the unified model were true, and the hidden black holes are simply blocked from view by doughnuts in the edge-on configuration, then researchers would expect them to cluster in the same way as the exposed ones. According to theory, since the doughnut structures would take on random orientations, the black holes should also be distributed randomly. It is like tossing a bunch of glazed doughnuts in the air -- roughly the same percentage of doughnuts always will be positioned in the edge-on and face-on positions, regardless of whether they are tightly clumped or spread far apart.
But WISE found something totally unexpected. The results showed the galaxies with hidden black holes are more clumped together than those of the exposed black holes. If these findings are confirmed, scientists will have to adjust the unified model and come up with new ways to explain why some black holes appear hidden.
"The main purpose of unification was to put a zoo of different kinds of active nuclei under a single umbrella," said Donoso. Now, that has become increasingly complex to do as we dig deeper into the WISE data."
Another way to understand the WISE results involves dark matter. Dark matter is an invisible substance that dominates matter in the universe, outweighing the regular matter that makes up people, planets and stars. Every galaxy sits in the center of a dark matter halo. Bigger halos have more gravity and, therefore, pull other galaxies toward them.
Because WISE found that the obscured black holes are more clustered than the others, the researchers know those hidden black holes reside in galaxies with larger dark matter halos. Though the halos themselves would not be responsible for hiding the black holes, they could be a clue about what is occurring.
"The unified theory was proposed to explain the complexity of what astronomers were seeing," said Stern. "It seems that simple model may have been too simple. As Einstein said, models should be made 'as simple as possible, but not simpler.'"
Scientists still are actively combing public data from WISE, which was put into hibernation in 2011 after scanning Earth's entire sky twice. WISE was reactivated in 2013, renamed NEOWISE, and given a new mission to identify potentially hazardous near-Earth objects.
For more information about NEOWISE, visit:
http://neo.jpl.nasa.gov/programs/neowise.html
For more information about WISE, visit:
http://www.nasa.gov/wise
NASA Mars Weathercam Helps Find Big New Crater
Gallery of shots is here.
Researchers have discovered on the Red Planet the largest fresh meteor-impact crater ever firmly documented with before-and-after images. The images were captured by NASA's Mars Reconnaissance Orbiter.
The crater spans half the length of a football field and first appeared in March 2012. The impact that created it likely was preceded by an explosion in the Martian sky caused by intense friction between an incoming asteroid and the planet's atmosphere. This series of events can be likened to the meteor blast that shattered windows in Chelyabinsk, Russia, last year. The air burst and ground impact darkened an area of the Martian surface about 5 miles (8 kilometers) across.
The darkened spot appears in images taken by the orbiter's weather-monitoring camera, the Mars Color Imager (MARCI). Images of the site from MARCI and from the two telescopic cameras on Mars Reconnaissance Orbiter are at:
http://go.usa.gov/8KgJ
Since the orbiter began its systematic observation of Mars in 2006, scientist Bruce Cantor has examined MARCI's daily global coverage, looking for evidence of dust storms and other observable weather events in the images. Cantor is this camera's deputy principal investigator at Malin Space Science Systems, the San Diego company that built and operates MARCI and the orbiter's telescopic Context Camera (CTX). Through his careful review of the images, he helps operators of NASA's solar-powered Mars rover, Opportunity, plan for weather events that may diminish the rover's energy. He also posts weekly Mars weather reports.
About two months ago, Cantor noticed an inconspicuous dark dot near the equator in one of the images.
"It wasn't what I was looking for," Cantor said. "I was doing my usual weather monitoring and something caught my eye. It looked usual, with rays emanating from a central spot."
He began examining earlier images, skipping back a month or more at a time. The images revealed that the dark spot was present a year ago, but not five years ago. He homed in further, checking images from about 40 different dates, and pinned down the date the impact event occurred; the spot was not there up through March 27, 2012, and then appeared before the daily imaging on March 28, 2012.
Once the dark spot was verified as new, it was targeted last month by CTX and the orbiter's sharpest-sighted camera, the High Resolution Imaging Science Experiment (HiRISE). Of the approximately 400 fresh crater-causing impacts on Mars that have been documented with before-and-after images, this is the only one discovered using a MARCI image, rather than an image from a higher-resolution camera.
CTX has imaged nearly the entire surface of Mars at least once during the orbiter's seven-plus years of observations. It had photographed the site of this newly-discovered crater in January 2012, prior to the impact. Two craters appear in the April 2014 CTX image that were not present in the earlier one, confirming the dark spot revealed by MARCI is related to a new impact crater.
HiRISE reveals more than a dozen smaller craters near the two larger ones seen in the CTX image, possibly created by chunks of the exploding asteroid or secondary impacts of material ejected from the main craters during impact. It also reveals many landslides that darkened slopes in the 5-mile surrounding area. A second HiRISE image in May 2014 added three-dimensional information.
"The biggest crater is unusual, quite shallow compared to other fresh craters we have observed," said HiRISE Principal Investigator Alfred McEwen of the University of Arizona, Tucson.
The largest crater is slightly elongated and spans 159 by 143 feet (48.5 by 43.5 meters).
McEwen estimates the impact object measured about 10 to 18 feet (3 to 5 meters) long, which is less than a third the estimated length of the asteroid that hit Earth's atmosphere near Chelyabinsk. Because Mars has much less atmosphere than Earth, space rocks of comparable size are more likely to penetrate to the surface of Mars and cause larger craters.
"Studies of fresh impact craters on Mars yield valuable information about impact rates and about subsurface material exposed by the excavations," said Leslie Tamppari, deputy project scientist for the Mars Reconnaissance Orbiter mission at NASA's Jet Propulsion Laboratory in Pasadena, California. "The combination of HiRISE and CTX has found and examined many of them, and now MARCI's daily coverage has given great precision about when a significant impact occurred."
NASA is developing concepts for its asteroid initiative to redirect a near-Earth asteroid -- possibly about the size of the rock that hit Mars on March 27 or 28, 2012 -- but much closer to Earth's distance from the sun. The project would involve a solar-powered spacecraft capturing a small asteroid or removing a piece of a larger asteroid, and redirecting it into a stable orbit around Earth's moon.
Astronauts will travel to the asteroid aboard NASA's Orion spacecraft, launched on the agency's Space Launch System rocket, to rendezvous with the captured asteroid. Once there, they would collect samples to return to Earth for study. This experience in human spaceflight beyond low-Earth orbit will help NASA test new systems and capabilities needed to send astronauts to Mars in the 2030s.
Pitch Black: Cosmic Clumps Cast the Darkest Shadows
The clumps represent the darkest portions of a huge, cosmic cloud of gas and dust located about 16,000 light-years away. A new study takes advantage of the shadows cast by these clumps to measure the cloud's structure and mass.
The dusty cloud, results suggest, will likely evolve into one of the most massive young clusters of stars in our galaxy. The densest clumps will blossom into the cluster's biggest, most powerful stars, called O-type stars, the formation of which has long puzzled scientists. These hulking stars have major impacts on their local stellar environments while also helping to create the heavy elements needed for life.
"The map of the structure of the cloud and its dense cores we have made in this study reveals a lot of fine details about the massive star and star cluster formation process," said Michael Butler, a postdoctoral researcher at the University of Zurich in Switzerland and lead author of the study, published in The Astrophysical Journal Letters.
The state-of-the-art map has helped pin down the cloud's mass to the equivalent of 70,000 suns packed into an area spanning about 50 light-years in diameter. The map comes courtesy of Spitzer observing in infrared light, which can more easily penetrate gas and dust than short-wavelength visible light. The effect is similar to that behind the deep red color of sunsets on smoggy days -- longer-wavelength red light more readily reaches our eyes through the haze, which scatters and absorbs shorter-wavelength blue light. In this case, however, the densest pockets of star-forming material within the cloud are so thick with dust that they scatter and block not only visible light, but also almost all background infrared light.
Observing in infrared lets scientists peer into otherwise inscrutable cosmic clouds and catch the early phases of star and star cluster formation. Typically, Spitzer detects infrared light emitted by young stars still shrouded in their dusty cocoons. For the new study, astronomers instead gauged the amount of background infrared light obscured by the cloud, using these shadows to infer where material had lumped together within the cloud. These blobs of gas and dust will eventually collapse gravitationally to make hundreds of thousands of new stars.
Most stars in the universe, perhaps our sun included, are thought to have formed en masse in these sorts of environments. Clusters of low-mass stars are quite common and well-studied. But clusters giving birth to higher-mass stars, like the cluster described here, are scarce and distant, which makes them harder to examine.
"In this rare kind of cloud, Spitzer has provided us with an important picture of massive star cluster formation caught in its earliest, embryonic stages," said Jonathan Tan, an associate professor of astronomy at the University of Florida, Gainesville, and co-author of the study.
The new findings will also help reveal how O-type stars form. O-type stars shine a brilliant white-blue, possess at least 16 times the sun's mass and have surface temperatures above 54,000 degrees Fahrenheit (30,000 degrees Celsius). These giant stars have a tremendous influence on their local stellar neighborhoods. Their winds and intense radiation blow away material that might draw together to create other stars and planetary systems. O-type stars are short-lived and quickly explode as supernovas, releasing enormous amounts of energy and forging the heavy elements needed to form planets and living organisms.
Researchers are not sure how, in O-type stars, it is possible for material to accumulate on scales of tens to 100 times the mass of our sun without dissipating or breaking down into multiple, smaller stars.
"We still do not have a settled theory or explanation of how these massive stars form," said Tan. "Therefore, detailed measurements of the birth clouds of future massive stars, as we have recorded in this study, are important for guiding new theoretical understanding."
Ganymede May Harbor 'Club Sandwich' of Oceans and Ice
The largest moon in our solar system, a companion to Jupiter named Ganymede, might have ice and oceans stacked up in several layers like a club sandwich, according to new NASA-funded research that models the moon's makeup.
Previously, the moon was thought to harbor a thick ocean sandwiched between just two layers of ice, one on top and one on bottom.
"Ganymede's ocean might be organized like a Dagwood sandwich," said Steve Vance of NASA's Jet Propulsion Laboratory in Pasadena, Calif., explaining the moon's resemblance to the "Blondie" cartoon character's multi-tiered sandwiches. The study, led by Vance, provides new theoretical evidence for the team's "club sandwich" model, first proposed last year. The research appears in the journal Planetary and Space Science.
The results support the idea that primitive life might have possibly arisen on the icy moon. Scientists say that places where water and rock interact are important for the development of life; for example, it's possible life began on Earth in bubbling vents on our sea floor. Prior to the new study, Ganymede's rocky sea bottom was thought to be coated with ice, not liquid -- a problem for the emergence of life. The "club sandwich" findings suggest otherwise: the first layer on top of the rocky core might be salty water.
"This is good news for Ganymede," said Vance. "Its ocean is huge, with enormous pressures, so it was thought that dense ice had to form at the bottom of the ocean. When we added salts to our models, we came up with liquids dense enough to sink to the sea floor."
NASA scientists first suspected an ocean in Ganymede in the 1970s, based on models of the large moon, which is bigger than Mercury. In the 1990s, NASA's Galileo mission flew by Ganymede, confirming the moon's ocean, and showing it extends to depths of hundreds of miles. The spacecraft also found evidence for salty seas, likely containing the salt magnesium sulfate.
Previous models of Ganymede's oceans assumed that salt didn't change the properties of liquid very much with pressure. Vance and his team showed, through laboratory experiments, how much salt really increases the density of liquids under the extreme conditions inside Ganymede and similar moons. It may seem strange that salt can make the ocean denser, but you can see for yourself how this works by adding plain old table salt to a glass of water. Rather than increasing in volume, the liquid shrinks and becomes denser. This is because the salt ions attract water molecules.
The models get more complicated when the different forms of ice are taken into account. The ice that floats in your drinks is called "Ice I." It's the least dense form of ice and lighter than water. But at high pressures, like those in crushingly deep oceans like Ganymede's, the ice crystal structures become more compact. "It's like finding a better arrangement of shoes in your luggage -- the ice molecules become packed together more tightly," said Vance. The ice can become so dense that it is heavier than water and falls to the bottom of the sea. The densest and heaviest ice thought to persist in Ganymede is called "Ice VI."
By modeling these processes using computers, the team came up with an ocean sandwiched between up to three ice layers, in addition to the rocky seafloor. The lightest ice is on top, and the saltiest liquid is heavy enough to sink to the bottom. What's more, the results demonstrate a possible bizarre phenomenon that causes the oceans to "snow upwards." As the oceans churn and cold plumes snake around, ice in the uppermost ocean layer, called "Ice III," could form in the seawater. When ice forms, salts precipitate out. The heavier salts would thus fall downward, and the lighter ice, or "snow," would float upward. This "snow" melts again before reaching the top of the ocean, possibly leaving slush in the middle of the moon sandwich.
"We don't know how long the Dagwood-sandwich structure would exist," said Christophe Sotin of JPL. "This structure represents a stable state, but various factors could mean the moon doesn't reach this stable state.
Sotin and Vance are both members of the Icy Worlds team at JPL, part of the multi-institutional NASA Astrobiology Institute based at the Ames Research Center in Moffett Field, Calif.
The results can be applied to exoplanets too, planets that circle stars beyond our sun. Some super-Earths, rocky planets more massive than Earth, have been proposed as "water worlds" covered in oceans. Could they have life? Vance and his team think laboratory experiments and more detailed modeling of exotic oceans might help find answers.
Ganymede is one of five moons in our solar system thought to support vast oceans beneath icy crusts. The other moons are Jupiter's Europa and Callisto and Saturn's Titan and Enceladus. The European Space Agency is developing a space mission, called JUpiter ICy moons Explorer or JUICE, to visit Europa, Callisto and Ganymede in the 2030s. NASA and JPL are contributing to three instruments on the mission, which is scheduled to launch in 2022 (see http://www.jpl.nasa.gov/news/news.php?release=2013-069).
Friday 15 August 2014
NASA's Spitzer, WISE Find Sun's Close, Cold Neighbor
NASA's Wide-field Infrared Survey Explorer (WISE) and Spitzer Space Telescope have discovered what appears to be the coldest "brown dwarf" known -- a dim, star-like body that surprisingly is as frosty as Earth's North Pole.
Images from the space telescopes also pinpointed the object's distance to 7.2 light-years away, earning it the title for fourth closest system to our sun. The closest system, a trio of stars, is Alpha Centauri, at about 4 light-years away.
"It's very exciting to discover a new neighbor of our solar system that is so close," said Kevin Luhman, an astronomer at Pennsylvania State University's Center for Exoplanets and Habitable Worlds, University Park. "And given its extreme temperature, it should tell us a lot about the atmospheres of planets, which often have similarly cold temperatures."
Brown dwarfs start their lives like stars, as collapsing balls of gas, but they lack the mass to burn nuclear fuel and radiate starlight. The newfound coldest brown dwarf is named WISE J085510.83-071442.5. It has a chilly temperature between minus 54 and 9 degrees Fahrenheit (minus 48 to minus 13 degrees Celsius). Previous record holders for coldest brown dwarfs, also found by WISE and Spitzer, were about room temperature.
WISE was able to spot the rare object because it surveyed the entire sky twice in infrared light, observing some areas up to three times. Cool objects like brown dwarfs can be invisible when viewed by visible-light telescopes, but their thermal glow -- even if feeble -- stands out in infrared light. In addition, the closer a body, the more it appears to move in images taken months apart. Airplanes are a good example of this effect: a closer, low-flying plane will appear to fly overhead more rapidly than a high-flying one.
"This object appeared to move really fast in the WISE data," said Luhman. "That told us it was something special."
After noticing the fast motion of WISE J085510.83-071442.5 in March of 2013, Luhman spent time analyzing additional images taken with Spitzer and the Gemini South telescope on Cerro Pachon in Chile. Spitzer's infrared observations helped determine the frosty temperature of the brown dwarf. Combined detections from WISE and Spitzer, taken from different positions around the sun, enabled the measurement of its distance through the parallax effect. This is the same principle that explains why your finger, when held out right in front of you, appears to jump from side to side when you alternate left- and right-eye views.
"It is remarkable that even after many decades of studying the sky, we still do not have a complete inventory of the sun's nearest neighbors," said Michael Werner, the project scientist for Spitzer at NASA's Jet Propulsion Laboratory in Pasadena, Calif. JPL manages and operates Spitzer. "This exciting new result demonstrates the power of exploring the universe using new tools, such as the infrared eyes of WISE and Spitzer."
WISE J085510.83-071442.5 is estimated to be 3 to 10 times the mass of Jupiter. With such a low mass, it could be a gas giant similar to Jupiter that was ejected from its star system. But scientists estimate it is probably a brown dwarf rather than a planet since brown dwarfs are known to be fairly common. If so, it is one of the least massive brown dwarfs known.
In March of 2013, Luhman's analysis of the images from WISE uncovered a pair of much warmer brown dwarfs at a distance of 6.5 light years, making that system the third closest to the sun. His search for rapidly moving bodies also demonstrated that the outer solar system probably does not contain a large, undiscovered planet, which has been referred to as "Planet X" or "Nemesis."
Images from the space telescopes also pinpointed the object's distance to 7.2 light-years away, earning it the title for fourth closest system to our sun. The closest system, a trio of stars, is Alpha Centauri, at about 4 light-years away.
"It's very exciting to discover a new neighbor of our solar system that is so close," said Kevin Luhman, an astronomer at Pennsylvania State University's Center for Exoplanets and Habitable Worlds, University Park. "And given its extreme temperature, it should tell us a lot about the atmospheres of planets, which often have similarly cold temperatures."
Brown dwarfs start their lives like stars, as collapsing balls of gas, but they lack the mass to burn nuclear fuel and radiate starlight. The newfound coldest brown dwarf is named WISE J085510.83-071442.5. It has a chilly temperature between minus 54 and 9 degrees Fahrenheit (minus 48 to minus 13 degrees Celsius). Previous record holders for coldest brown dwarfs, also found by WISE and Spitzer, were about room temperature.
WISE was able to spot the rare object because it surveyed the entire sky twice in infrared light, observing some areas up to three times. Cool objects like brown dwarfs can be invisible when viewed by visible-light telescopes, but their thermal glow -- even if feeble -- stands out in infrared light. In addition, the closer a body, the more it appears to move in images taken months apart. Airplanes are a good example of this effect: a closer, low-flying plane will appear to fly overhead more rapidly than a high-flying one.
"This object appeared to move really fast in the WISE data," said Luhman. "That told us it was something special."
After noticing the fast motion of WISE J085510.83-071442.5 in March of 2013, Luhman spent time analyzing additional images taken with Spitzer and the Gemini South telescope on Cerro Pachon in Chile. Spitzer's infrared observations helped determine the frosty temperature of the brown dwarf. Combined detections from WISE and Spitzer, taken from different positions around the sun, enabled the measurement of its distance through the parallax effect. This is the same principle that explains why your finger, when held out right in front of you, appears to jump from side to side when you alternate left- and right-eye views.
"It is remarkable that even after many decades of studying the sky, we still do not have a complete inventory of the sun's nearest neighbors," said Michael Werner, the project scientist for Spitzer at NASA's Jet Propulsion Laboratory in Pasadena, Calif. JPL manages and operates Spitzer. "This exciting new result demonstrates the power of exploring the universe using new tools, such as the infrared eyes of WISE and Spitzer."
WISE J085510.83-071442.5 is estimated to be 3 to 10 times the mass of Jupiter. With such a low mass, it could be a gas giant similar to Jupiter that was ejected from its star system. But scientists estimate it is probably a brown dwarf rather than a planet since brown dwarfs are known to be fairly common. If so, it is one of the least massive brown dwarfs known.
In March of 2013, Luhman's analysis of the images from WISE uncovered a pair of much warmer brown dwarfs at a distance of 6.5 light years, making that system the third closest to the sun. His search for rapidly moving bodies also demonstrated that the outer solar system probably does not contain a large, undiscovered planet, which has been referred to as "Planet X" or "Nemesis."
NASA's Kepler Telescope Discovers First Earth-Size Planet in 'Habitable Zone'
While planets have previously been found in the habitable zone, they are all at least 40 percent larger in size than Earth, and understanding their makeup is challenging. Kepler-186f is more reminiscent of Earth.
"The discovery of Kepler-186f is a significant step toward finding worlds like our planet Earth," said Paul Hertz, NASA's Astrophysics Division director at the agency's headquarters in Washington. "Future NASA missions, like the Transiting Exoplanet Survey Satellite and the James Webb Space Telescope, will discover the nearest rocky exoplanets and determine their composition and atmospheric conditions, continuing humankind's quest to find truly Earth-like worlds."
Although the size of Kepler-186f is known, its mass and composition are not. Previous research, however, suggests that a planet the size of Kepler-186f is likely to be rocky.
"We know of just one planet where life exists -- Earth. When we search for life outside our solar system, we focus on finding planets with characteristics that mimic that of Earth," said Elisa Quintana, research scientist at the SETI Institute at NASA's Ames Research Center in Moffett Field, Calif., and lead author of the paper published today in the journal Science. "Finding a habitable zone planet comparable to Earth in size is a major step forward."
Kepler-186f resides in the Kepler-186 system, about 500 light-years from Earth in the constellation Cygnus. The system is also home to four companion planets, which orbit a star half the size and mass of our sun. The star is classified as an M dwarf, or red dwarf, a class of stars that makes up 70 percent of the stars in the Milky Way galaxy.
"M dwarfs are the most numerous stars," said Quintana. "The first signs of other life in the galaxy may well come from planets orbiting an M dwarf."
Kepler-186f orbits its star once every 130 days and receives one-third the energy from its star that Earth gets from the sun, placing it nearer the outer edge of the habitable zone. On the surface of Kepler-186f, the brightness of its star at high noon is only as bright as our sun appears to us about an hour before sunset.
"Being in the habitable zone does not mean we know this planet is habitable. The temperature on the planet is strongly dependent on what kind of atmosphere the planet has," said Thomas Barclay, research scientist at the Bay Area Environmental Research Institute at Ames, and co-author of the paper. "Kepler-186f can be thought of as an Earth-cousin rather than an Earth-twin. It has many properties that resemble Earth."
The four companion planets, Kepler-186b, Kepler-186c, Kepler-186d and Kepler-186e, whiz around their sun every four, seven, 13 and 22 days, respectively, making them too hot for life as we know it. These four inner planets all measure less than 1.5 times the size of Earth.
The next steps in the search for distant life include looking for true Earth-twins -- Earth-size planets orbiting within the habitable zone of a sun-like star -- and measuring their chemical compositions. The Kepler Space Telescope, which simultaneously and continuously measured the brightness of more than 150,000 stars, is NASA's first mission capable of detecting Earth-size planets around stars like our sun
NASA Cassini Images May Reveal Birth of a Saturn Moon
NASA's Cassini spacecraft has documented the formation of a small icy object within the rings of Saturn that may be a new moon, and may also provide clues to the formation of the planet's known moons.
Images taken with Cassini's narrow angle camera on April 15, 2013, show disturbances at the very edge of Saturn's A ring -- the outermost of the planet's large, bright rings. One of these disturbances is an arc about 20 percent brighter than its surroundings, 750 miles (1,200 kilometers) long and 6 miles (10 kilometers) wide. Scientists also found unusual protuberances in the usually smooth profile at the ring's edge. Scientists believe the arc and protuberances are caused by the gravitational effects of a nearby object. Details of the observations were published online today (April 14, 2014) by the journal Icarus.
The object is not expected to grow any larger, and may even be falling apart. But the process of its formation and outward movement aids in our understanding of how Saturn's icy moons, including the cloud-wrapped Titan and ocean-holding Enceladus, may have formed in more massive rings long ago. It also provides insight into how Earth and other planets in our solar system may have formed and migrated away from our star, the sun.
"We have not seen anything like this before," said Carl Murray of Queen Mary University of London, the report's lead author. "We may be looking at the act of birth, where this object is just leaving the rings and heading off to be a moon in its own right."
The object, informally named Peggy, is too small to be seen in images so far. Scientists estimate it is probably no more than about a half mile (about a kilometer) in diameter. Saturn's icy moons range in size depending on their proximity to the planet -- the farther from the planet, the larger. And many of Saturn's moons are composed primarily of ice, as are the particles that form Saturn's rings. Based on these facts, and other indicators, researchers recently proposed that the icy moons formed from ring particles and then moved outward, away from the planet, merging with other moons on the way.
"Witnessing the possible birth of a tiny moon is an exciting, unexpected event," said Cassini Project Scientist Linda Spilker, of NASA's Jet Propulsion Laboratory in Pasadena, Calif. According to Spilker, Cassini's orbit will move closer to the outer edge of the A ring in late 2016 and provide an opportunity to study Peggy in more detail and perhaps even image it.
It is possible the process of moon formation in Saturn's rings has ended with Peggy, as Saturn's rings now are, in all likelihood, too depleted to make more moons. Because they may not observe this process again, Murray and his colleagues are wringing from the observations all they can learn.
"The theory holds that Saturn long ago had a much more massive ring system capable of giving birth to larger moons," Murray said. "As the moons formed near the edge, they depleted the rings and evolved, so the ones that formed earliest are the largest and the farthest out."
NASA Space Assets Detect Ocean inside Saturn Moon
Researchers theorized the presence of an interior reservoir of water in 2005 when Cassini discovered water vapor and ice spewing from vents near the moon's south pole. The new data provide the first geophysical measurements of the internal structure of Enceladus, consistent with the existence of a hidden ocean inside the moon. Findings from the gravity measurements are in the Friday, April 4 edition of the journal Science.
"The way we deduce gravity variations is a concept in physics called the Doppler Effect, the same principle used with a speed-measuring radar gun," said Sami Asmar of NASA's Jet Propulsion Laboratory in Pasadena, Calif., a coauthor of the paper. "As the spacecraft flies by Enceladus, its velocity is perturbed by an amount that depends on variations in the gravity field that we're trying to measure. We see the change in velocity as a change in radio frequency, received at our ground stations here all the way across the solar system."
The gravity measurements suggest a large, possibly regional, ocean about 6 miles (10 kilometers) deep, beneath an ice shell about 19 to 25 miles (30 to 40 kilometers) thick. The subsurface ocean evidence supports the inclusion of Enceladus among the most likely places in our solar system to host microbial life. Before Cassini reached Saturn in July 2004, no version of that short list included this icy moon, barely 300 miles (500 kilometers) in diameter.
"This then provides one possible story to explain why water is gushing out of these fractures we see at the south pole," said David Stevenson of the California Institute of Technology, Pasadena, one of the paper's co-authors.
Cassini has flown near Enceladus 19 times. Three flybys, from 2010 to 2012, yielded precise trajectory measurements. The gravitational tug of a planetary body, such as Enceladus, alters a spacecraft's flight path. Variations in the gravity field, such as those caused by mountains on the surface or differences in underground composition, can be detected as changes in the spacecraft's velocity, measured from Earth.
The technique of analyzing a radio signal between Cassini and the Deep Space Network can detect changes in velocity as small as less than one foot per hour (90 microns per second). With this precision, the flyby data yielded evidence of a zone inside the southern end of the moon with higher density than other portions of the interior.
The south pole area has a surface depression that causes a dip in the local tug of gravity. However, the magnitude of the dip is less than expected given the size of the depression, leading researchers to conclude the depression's effect is partially offset by a high-density feature in the region, beneath the surface.
"The Cassini gravity measurements show a negative gravity anomaly at the south pole that however is not as large as expected from the deep depression detected by the onboard camera," said the paper's lead author, Luciano Iess of Sapienza University of Rome. "Hence the conclusion that there must be a denser material at depth that compensates the missing mass: very likely liquid water, which is seven percent denser than ice. The magnitude of the anomaly gave us the size of the water reservoir."
There is no certainty the subsurface ocean supplies the water plume spraying out of surface fractures near the south pole of Enceladus, however, scientists reason it is a real possibility. The fractures may lead down to a part of the moon that is tidally heated by the moon's repeated flexing, as it follows an eccentric orbit around Saturn.
Much of the excitement about the Cassini mission's discovery of the Enceladus water plume stems from the possibility that it originates from a wet environment that could be a favorable environment for microbial life.
"Material from Enceladus' south polar jets contains salty water and organic molecules, the basic chemical ingredients for life," said Linda Spilker, Cassini's project scientist at JPL. "Their discovery expanded our view of the 'habitable zone' within our solar system and in planetary systems of other stars. This new validation that an ocean of water underlies the jets furthers understanding about this intriguing environment."
Mystery of Planet-forming Disks Explained by Magnetism
Astronomers say that magnetic storms in the gas orbiting young stars may explain a mystery that has persisted since before 2006.
Researchers using NASA's Spitzer Space Telescope to study developing stars have had a hard time figuring out why the stars give off more infrared light than expected. The planet-forming disks that circle the young stars are heated by starlight and glow with infrared light, but Spitzer detected additional infrared light coming from an unknown source.
A new theory, based on three-dimensional models of planet-forming disks, suggests the answer: Gas and dust suspended above the disks on gigantic magnetic loops like those seen on the sun absorb the starlight and glow with infrared light.
"If you could somehow stand on one of these planet-forming disks and look at the star in the center through the disk atmosphere, you would see what looks like a sunset," said Neal Turner of NASA's Jet Propulsion Laboratory, Pasadena, Calif.
The new models better describe how planet-forming material around stars is stirred up, making its way into future planets, asteroids and comets.
While the idea of magnetic atmospheres on planet-forming disks is not new, this is the first time they have been linked to the mystery of the observed excess infrared light. According to Turner and colleagues, the magnetic atmospheres are similar to what takes place on the surface of our sun, where moving magnetic field lines spur tremendous solar prominences to flare up in big loops.
Stars are born out of collapsing pockets in enormous clouds of gas and dust, rotating as they shrink down under the pull of gravity. As a star grows in size, more material rains down toward it from the cloud, and the rotation flattens this material out into a turbulent disk. Ultimately, planets clump together out of the disk material.
In the 1980s, the Infrared Astronomical Satellite mission, a joint project that included NASA, began finding more infrared light than expected around young stars. Using data from other telescopes, astronomers pieced together the presence of dusty disks of planet-forming material. But eventually it became clear the disks alone weren't enough to account for the extra infrared light -- especially in the case of stars a few times the mass of the sun.
One theory introduced the idea that instead of a disk, the stars were surrounded by a giant dusty halo, which intercepted the star's visible light and re-radiated it at infrared wavelengths. Then, recent observations from ground-based telescopes suggested that both a disk and a halo were needed. Finally, three-dimensional computer modeling of the turbulence in the disks showed the disks ought to have fuzzy surfaces, with layers of low-density gas supported by magnetic fields, similar to the way solar prominences are supported by the sun's magnetic field.
The new work brings these pieces together by calculating how the starlight falls across the disk and its fuzzy atmosphere. The result is that the atmosphere absorbs and re-radiates enough to account for all the extra infrared light.
"The starlight-intercepting material lies not in a halo, and not in a traditional disk either, but in a disk atmosphere supported by magnetic fields," said Turner. "Such magnetized atmospheres were predicted to form as the disk drives gas inward to crash onto the growing star."
Over the next few years, astronomers will further test these ideas about the structure of the disk atmospheres by using giant ground-based telescopes linked together as interferometers. An interferometer combines and processes data from multiple telescopes to show details finer than each telescope can see alone. Spectra of the turbulent gas in the disks will also come from NASA's SOFIA telescope, the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile, and from NASA's James Webb Space Telescope after its launch in 2018.
Researchers using NASA's Spitzer Space Telescope to study developing stars have had a hard time figuring out why the stars give off more infrared light than expected. The planet-forming disks that circle the young stars are heated by starlight and glow with infrared light, but Spitzer detected additional infrared light coming from an unknown source.
A new theory, based on three-dimensional models of planet-forming disks, suggests the answer: Gas and dust suspended above the disks on gigantic magnetic loops like those seen on the sun absorb the starlight and glow with infrared light.
"If you could somehow stand on one of these planet-forming disks and look at the star in the center through the disk atmosphere, you would see what looks like a sunset," said Neal Turner of NASA's Jet Propulsion Laboratory, Pasadena, Calif.
The new models better describe how planet-forming material around stars is stirred up, making its way into future planets, asteroids and comets.
While the idea of magnetic atmospheres on planet-forming disks is not new, this is the first time they have been linked to the mystery of the observed excess infrared light. According to Turner and colleagues, the magnetic atmospheres are similar to what takes place on the surface of our sun, where moving magnetic field lines spur tremendous solar prominences to flare up in big loops.
Stars are born out of collapsing pockets in enormous clouds of gas and dust, rotating as they shrink down under the pull of gravity. As a star grows in size, more material rains down toward it from the cloud, and the rotation flattens this material out into a turbulent disk. Ultimately, planets clump together out of the disk material.
In the 1980s, the Infrared Astronomical Satellite mission, a joint project that included NASA, began finding more infrared light than expected around young stars. Using data from other telescopes, astronomers pieced together the presence of dusty disks of planet-forming material. But eventually it became clear the disks alone weren't enough to account for the extra infrared light -- especially in the case of stars a few times the mass of the sun.
One theory introduced the idea that instead of a disk, the stars were surrounded by a giant dusty halo, which intercepted the star's visible light and re-radiated it at infrared wavelengths. Then, recent observations from ground-based telescopes suggested that both a disk and a halo were needed. Finally, three-dimensional computer modeling of the turbulence in the disks showed the disks ought to have fuzzy surfaces, with layers of low-density gas supported by magnetic fields, similar to the way solar prominences are supported by the sun's magnetic field.
The new work brings these pieces together by calculating how the starlight falls across the disk and its fuzzy atmosphere. The result is that the atmosphere absorbs and re-radiates enough to account for all the extra infrared light.
"The starlight-intercepting material lies not in a halo, and not in a traditional disk either, but in a disk atmosphere supported by magnetic fields," said Turner. "Such magnetized atmospheres were predicted to form as the disk drives gas inward to crash onto the growing star."
Over the next few years, astronomers will further test these ideas about the structure of the disk atmospheres by using giant ground-based telescopes linked together as interferometers. An interferometer combines and processes data from multiple telescopes to show details finer than each telescope can see alone. Spectra of the turbulent gas in the disks will also come from NASA's SOFIA telescope, the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile, and from NASA's James Webb Space Telescope after its launch in 2018.
Stardust Discovers Potential Interstellar Space Particles
Seven rare, microscopic interstellar dust particles that date to the beginnings of the solar system are among the samples collected by scientists who have been studying the payload from NASA's Stardust spacecraft since its return to Earth in 2006. If confirmed, these particles would be the first samples of contemporary interstellar dust.
A team of scientists has been combing through the spacecraft's aerogel and aluminum foil dust collectors since Stardust returned in 2006.The seven particles probably came from outside our solar system, perhaps created in a supernova explosion millions of years ago and altered by exposure to the extreme space environment. The particles would be the first confirmed samples of contemporary interstellar dust.
The research report appears in the Aug. 15 issue of the journal Science. Twelve other papers about the particles will appear next week in the journal Meteoritics & Planetary Science.
"These are the most challenging objects we will ever have in the lab for study, and it is a triumph that we have made as much progress in their analysis as we have," said Michael Zolensky, curator of the Stardust laboratory at NASA's Johnson Space Center in Houston and coauthor of the Science paper.
Stardust was launched in 1999 and returned to Earth on Jan. 15, 2006, at the Utah Test and Training Range, 80 miles west of Salt Lake City. The Stardust Sample Return Canister was transported to a curatorial facility at Johnson where the Stardust collectors remain preserved and protected for scientific study.
Inside the canister, a tennis racket-like sample collector tray captured the particles in silica aerogel as the spacecraft flew within 149 miles (about 240 kilometers) of a comet in January 2004. An opposite side of the tray holds interstellar dust particles captured by the spacecraft during its seven-year, three-billion-mile journey.
Scientists caution that additional tests must be done before they can say definitively that these are pieces of debris from interstellar space. But if they are, the particles could help explain the origin and evolution of interstellar dust.
The particles are much more diverse in terms of chemical composition and structure than scientists expected. The smaller particles differ greatly from the larger ones and appear to have varying histories. Many of the larger particles have been described as having a fluffy structure, similar to a snowflake.
Two particles, each only about two microns (thousandths of a millimeter) in diameter, were isolated after their tracks were discovered by a group of citizen scientists. These volunteers, who call themselves "Dusters," scanned more than a million images as part of a University of California, Berkeley, citizen-science project, which proved critical to finding these needles in a haystack.
A third track, following the direction of the wind during flight, was left by a particle that apparently was moving so fast -- more than 10 miles per second (15 kilometers per second) -- that it vaporized. Volunteers identified tracks left by another 29 particles that were determined to have been kicked out of the spacecraft into the collectors.
Four of the particles reported in Science were found in aluminum foils between tiles on the collector tray. Although the foils were not originally planned as dust collection surfaces, an international team led by physicist Rhonda Stroud of the Naval Research Laboratory searched the foils and identified four pits lined with material composed of elements that fit the profile of interstellar dust particles.
Three of these four particles, just a few tenths of a micron across, contained sulfur compounds, which some astronomers have argued do not occur in interstellar dust. A preliminary examination team plans to continue analysis of the remaining 95 percent of the foils to possibly find enough particles to understand the variety and origins of interstellar dust.
Supernovas, red giants and other evolved stars produce interstellar dust and generate heavy elements like carbon, nitrogen and oxygen necessary for life. Two particles, dubbed Orion and Hylabrook, will undergo further tests to determine their oxygen isotope quantities, which could provide even stronger evidence for their extrasolar origin.
Scientists at Johnson have scanned half the panels at various depths and turned these scans into movies, which were then posted online, where the Dusters could access the footage to search for particle tracks.
Once several Dusters tag a likely track, Andrew Westphal, lead author of the Science article, and his team verify the identifications. In the one million frames scanned so far, each a half-millimeter square, Dusters have found 69 tracks, while Westphal has found two. Thirty-one of these were extracted along with surrounding aerogel by scientists at Johnson and shipped to UC Berkeley to be analyzed
A team of scientists has been combing through the spacecraft's aerogel and aluminum foil dust collectors since Stardust returned in 2006.The seven particles probably came from outside our solar system, perhaps created in a supernova explosion millions of years ago and altered by exposure to the extreme space environment. The particles would be the first confirmed samples of contemporary interstellar dust.
The research report appears in the Aug. 15 issue of the journal Science. Twelve other papers about the particles will appear next week in the journal Meteoritics & Planetary Science.
"These are the most challenging objects we will ever have in the lab for study, and it is a triumph that we have made as much progress in their analysis as we have," said Michael Zolensky, curator of the Stardust laboratory at NASA's Johnson Space Center in Houston and coauthor of the Science paper.
Stardust was launched in 1999 and returned to Earth on Jan. 15, 2006, at the Utah Test and Training Range, 80 miles west of Salt Lake City. The Stardust Sample Return Canister was transported to a curatorial facility at Johnson where the Stardust collectors remain preserved and protected for scientific study.
Inside the canister, a tennis racket-like sample collector tray captured the particles in silica aerogel as the spacecraft flew within 149 miles (about 240 kilometers) of a comet in January 2004. An opposite side of the tray holds interstellar dust particles captured by the spacecraft during its seven-year, three-billion-mile journey.
Scientists caution that additional tests must be done before they can say definitively that these are pieces of debris from interstellar space. But if they are, the particles could help explain the origin and evolution of interstellar dust.
The particles are much more diverse in terms of chemical composition and structure than scientists expected. The smaller particles differ greatly from the larger ones and appear to have varying histories. Many of the larger particles have been described as having a fluffy structure, similar to a snowflake.
Two particles, each only about two microns (thousandths of a millimeter) in diameter, were isolated after their tracks were discovered by a group of citizen scientists. These volunteers, who call themselves "Dusters," scanned more than a million images as part of a University of California, Berkeley, citizen-science project, which proved critical to finding these needles in a haystack.
A third track, following the direction of the wind during flight, was left by a particle that apparently was moving so fast -- more than 10 miles per second (15 kilometers per second) -- that it vaporized. Volunteers identified tracks left by another 29 particles that were determined to have been kicked out of the spacecraft into the collectors.
Four of the particles reported in Science were found in aluminum foils between tiles on the collector tray. Although the foils were not originally planned as dust collection surfaces, an international team led by physicist Rhonda Stroud of the Naval Research Laboratory searched the foils and identified four pits lined with material composed of elements that fit the profile of interstellar dust particles.
Three of these four particles, just a few tenths of a micron across, contained sulfur compounds, which some astronomers have argued do not occur in interstellar dust. A preliminary examination team plans to continue analysis of the remaining 95 percent of the foils to possibly find enough particles to understand the variety and origins of interstellar dust.
Supernovas, red giants and other evolved stars produce interstellar dust and generate heavy elements like carbon, nitrogen and oxygen necessary for life. Two particles, dubbed Orion and Hylabrook, will undergo further tests to determine their oxygen isotope quantities, which could provide even stronger evidence for their extrasolar origin.
Scientists at Johnson have scanned half the panels at various depths and turned these scans into movies, which were then posted online, where the Dusters could access the footage to search for particle tracks.
Once several Dusters tag a likely track, Andrew Westphal, lead author of the Science article, and his team verify the identifications. In the one million frames scanned so far, each a half-millimeter square, Dusters have found 69 tracks, while Westphal has found two. Thirty-one of these were extracted along with surrounding aerogel by scientists at Johnson and shipped to UC Berkeley to be analyzed
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