When NASA's Juno mission arrives at Jupiter on July 4, 2016, new views of the giant planet's swirling clouds will be sent back to Earth, courtesy of its color camera, called JunoCam. But unlike previous space missions, professional scientists will not be the ones producing the processed views, or even choosing which images to capture. Instead, the public will act as a virtual imaging team, participating in key steps of the process, from identifying features of interest to sharing the finished images online.
"This is really the public's camera. We are hoping students and whole classrooms will get involved and join our team," said Scott Bolton, Juno principal investigator at the Southwest Research Institute in San Antonio.
The Juno team has kicked off the first stage of JunoCam activity with the launch of a new Web platform on the mission's website. Now and throughout the mission, amateur astronomers are invited to submit images of Jupiter from their own telescopes. These views will be the basis for online discussions about which of Jupiter's swirls, bands and spots JunoCam should image as it makes repeated, close passes over the planet. The ground-based views will be essential for identifying and tracking changes in the planet's cloud features as Juno approaches.
"In between our close Jupiter flybys, Juno goes far from the planet, and Jupiter will shrink in JunoCam's field of view to a size too small to be useful for choosing which features to capture. So we really are counting on having help from ground-based observers," said Candy Hansen, a member of the Juno science team who leads planning for the camera.
Juno will get closer to Jupiter than any previous orbiting spacecraft, giving JunoCam the best close-up views yet of the planet's colorful cloud bands. Every 14 days, the spinning, solar-powered spacecraft will dive past the planet in just a couple of hours, gathering huge amounts of science data, plus about a dozen JunoCam images. At closest approach, Juno will snap photos from only 3,100 miles (5,000 kilometers) above Jupiter's clouds.
"JunoCam will capture high-resolution color views of Jupiter's bands, but that's only part of the story," said Diane Brown, Juno program executive at NASA Headquarters in Washington. "We'll also be treated to the first-ever views of Jupiter's north and south poles, which have never been imaged before."
Unlike most spacecraft cameras, JunoCam was specially designed to work on a spinning spacecraft. Typically, spacecraft must point very precisely at their subjects while taking a picture to avoid smearing their images. Since Juno rotates twice per minute, the Juno team designed a camera that images several lines of pixels at a time, at the right speed to cancel out the rotation and avoid smear.
Previously, the best images of Jupiter were taken by NASA's two Voyager spacecraft, which flew past the planet in 1979. JunoCam's field of view is much wider than that of Voyager's narrow-angle camera. This means every JunoCam image is a kind of panorama, and its highest-resolution images will show wide swaths of clouds. The camera also benefits from decades of technology advancement, making it lighter, less power-hungry and lower in cost.
After JunoCam data arrive on Earth, members of the public will process the images to create color pictures. The Juno team successfully tested this approach when JunoCam acquired its first high-resolution views, showing our home planet during the spacecraft's Earth flyby in October 2013.
Since the mission's beginnings, JunoCam was intended almost entirely as a public outreach tool, in contrast to the spacecraft's other instruments that will address Juno's core science questions. Juno scientists will ensure JunoCam returns a few great shots of Jupiter's polar regions, but the overwhelming majority of the camera's image targets will be chosen by the public, with the data being processed by them as well.
"We want to give people an opportunity to participate with NASA, and public involvement is key to JunoCam's success," said Bolton. "This is citizen science at its best."
Information about JunoCam's new features for amateur astronomer engagement is available at:
The JunoCam Web platform will soon add a discussion section to begin identifying features of interest on the planet for JunoCam to image.
The Juno mission website, designed and developed by Radical Media since 2011, has been augmented and updated to include new features in addition to the site's interactive JunoCam section.
Launched in 2011, the Juno mission uses every known technique to probe beneath the obscuring cloud cover of Jupiter to learn more about the planet's origins, structure, atmosphere and magnetosphere.
NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. Juno is part of NASA's New Frontiers Program, which is managed at NASA's Marshall Space Flight Center in Huntsville, Alabama. Lockheed Martin Space Systems, Denver, built the spacecraft. JPL is a division of the California Institute of Technology, in Pasadena, which manages the laboratory for NASA.
For more information about Juno visit:
Tuesday, 22 March 2016
How a dying star spreads its seed
During their death throes, as they are running out of fuel for the nuclear furnace in their cores, giant stars swell up to enormous size and eject huge amounts of gas and dust into space. But what drives out all that material? Radiation pressure is the main suspect, the idea being that photons from the star hit the dust grains, propelling them out into space. But typical grains of interstellar dust are just too small: At about a hundred-millionth of a meter, they just don’t catch enough photons. Now, a team using an instrument called SPHERE on the European Southern Observatory’s Very Large Telescope in Chile has found the answer. SPHERE was designed to directly observe planets around other stars, so it’s equipped with a mask to blot out the light from a star so that fainter things around it can be seen. The team used the instrument to observe the surroundings of the hypergiant star VY Canis Majoris (pictured) which is up to 40 times the mass of our sun and 300,000 times as luminous. As the researchers report this week in Astronomy & Astrophysics, they found that VY Canis Majoris is surrounded by dust grains 50 times larger than normal, giving them enough surface area to be successfully pushed away by the star’s radiation pressure. This explains how the dust ends up far out in space and, after the star has exploded as a supernova and dispersed more material, provides the seed material for a later generation of stars and planets.
Loss of Carbon in Martian Atmosphere Explained
The solar wind stripped away much of Mars' ancient atmosphere and is still removing tons of it every day. But scientists have been puzzled by why they haven't found more carbon -- in the form of carbonate -- captured into Martian rocks. They have also sought to explain the ratio of heavier and lighter carbons in the modern Martian atmosphere.
Now a team of scientists from the California Institute of Technology and NASA's Jet Propulsion Laboratory, both in Pasadena, offer an explanation of the "missing" carbon, in a paper published today by the journal Nature Communications.
They suggest that 3.8 billion years ago, Mars might have had a moderately dense atmosphere. Such an atmosphere -- with a surface pressure equal to or less than that found on Earth -- could have evolved into the current thin one, not only minus the "missing" carbon problem, but also in a way consistent with the observed ratio of carbon-13 to carbon-12, which differ only by how many neutrons are in each nucleus.
"Our paper shows that transitioning from a moderately dense atmosphere to the current thin one is entirely possible," says Caltech postdoctoral fellow Renyu Hu, the lead author. "It is exciting that what we know about the Martian atmosphere can now be pieced together into a consistent picture of its evolution -- and this does not require a massive undetected carbon reservoir."
When considering how the early Martian atmosphere might have transitioned to its current state, there are two possible mechanisms for the removal of the excess carbon dioxide. Either the carbon dioxide was incorporated into minerals in rocks called carbonates or it was lost to space.
An August 2015 study used data from several Mars-orbiting spacecraft to inventory carbonates, showing there are nowhere near enough in the upper half mile (one kilometer) or the crust to contain the missing carbon from a thick early atmosphere during a time when networks of ancient river channels were active, about 3.8 billion years ago.
The escaped-to-space scenario has also been problematic. Because various processes can change the relative amounts of carbon-13 to carbon-12 isotopes in the atmosphere, "we can use these measurements of the ratio at different points in time as a fingerprint to infer exactly what happened to the Martian atmosphere in the past," says Hu. The first constraint is set by measurements of the ratio in meteorites that contain gases released volcanically from deep inside Mars, providing insight into the starting isotopic ratio of the original Martian atmosphere. The modern ratio comes from measurements by the SAM (Sample Analysis at Mars) instrument on NASA's Curiosity rover.
One way carbon dioxide escapes to space from Mars' atmosphere is called sputtering, which involves interactions between the solar wind and the upper atmosphere. NASA's MAVEN (Mars Atmosphere and Volatile Evolution) mission has yielded recent results indicating that about a quarter pound (about 100 grams) of particles every second are stripped from today's Martian atmosphere via this process, likely the main driver of atmospheric loss. Sputtering slightly favors loss of carbon-12, compared to carbon-13, but this effect is small. The Curiosity measurement shows that today's Martian atmosphere is far more enriched in carbon-13 -- in proportion to carbon-12 -- than it should be as a result of sputtering alone, so a different process must also be at work.
Hu and his co-authors identify a mechanism that could have significantly contributed to the carbon-13 enrichment. The process begins with ultraviolet (UV) light from the sun striking a molecule of carbon dioxide in the upper atmosphere, splitting it into carbon monoxide and oxygen. Then, UV light hits the carbon monoxide and splits it into carbon and oxygen. Some carbon atoms produced this way have enough energy to escape from the atmosphere, and the new study shows that carbon-12 is far more likely to escape than carbon-13.
Modeling the long-term effects of this "ultraviolet photodissociation" mechanism, the researchers found that a small amount of escape by this process leaves a large fingerprint in the carbon isotopic ratio. That, in turn, allowed them to calculate that the atmosphere 3.8 billion years ago might have had a surface pressure a bit less thick than Earth's atmosphere today.
"This solves a long-standing paradox," said Bethany Ehlmann of Caltech and JPL, a co-author of both today's publication and the August one about carbonates. "The supposed very thick atmosphere seemed to imply that you needed this big surface carbon reservoir, but the efficiency of the UV photodissociation process means that there actually is no paradox. You can use normal loss processes as we understand them, with detected amounts of carbonate, and find an evolutionary scenario for Mars that makes sense."
Strange Star Likely Swarmed by Comets (NASA Nov 2015)
A star called KIC 8462852 has been in the news recently for unexplained and bizarre behavior. NASA's Kepler mission had monitored the star for four years, observing two unusual incidents, in 2011 and 2013, when the star's light dimmed in dramatic, never-before-seen ways. Something had passed in front of the star and blocked its light, but what?
Scientists first reported the findings in September, suggesting a family of comets as the most likely explanation. Other cited causes included fragments of planets and asteroids.
A new study using data from NASA's Spitzer Space Telescope addresses the mystery, finding more evidence for the scenario involving a swarm of comets. The study, led by Massimo Marengo of Iowa State University, Ames, is accepted for publication in the Astrophysical Journal Letters.
One way to learn more about the star is to study it in infrared light. Kepler had observed it in visible light. If a planetary impact, or a collision amongst asteroids, were behind the mystery of KIC 8462852, then there should be an excess of infrared light around the star. Dusty, ground-up bits of rock would be at the right temperature to glow at infrared wavelengths.
At first, researchers tried to look for infrared light using NASA's Wide-Field Infrared Survey Explorer, or WISE, and found none. But those observations were taken in 2010, before the strange events seen by Kepler -- and before any collisions would have kicked up dust.
To search for infrared light that might have been generated after the oddball events, researchers turned to Spitzer, which, like WISE, also detects infrared light. Spitzer just happened to observe KIC 8462852 more recently in 2015.
"Spitzer has observed all of the hundreds of thousands of stars where Kepler hunted for planets, in the hope of finding infrared emission from circumstellar dust," said Michael Werner, the Spitzer project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, and the lead investigator of that particular Spitzer/Kepler observing program.
But, like WISE, Spitzer did not find any significant excess of infrared light from warm dust. That makes theories of rocky smashups very unlikely, and favors the idea that cold comets are responsible. It's possible that a family of comets is traveling on a very long, eccentric orbit around the star. At the head of the pack would be a very large comet, which would have blocked the star's light in 2011, as noted by Kepler. Later, in 2013, the rest of the comet family, a band of varied fragments lagging behind, would have passed in front of the star and again blocked its light.
By the time Spitzer observed the star in 2015, those comets would be farther away, having continued on their long journey around the star. They would not leave any infrared signatures that could be detected.
According to Marengo, more observations are needed to help settle the case of KIC 8462852.
"This is a very strange star," he said. "It reminds me of when we first discovered pulsars. They were emitting odd signals nobody had ever seen before, and the first one discovered was named LGM-1 after 'Little Green Men.'"
In the end, the LGM-1 signals turned out to be a natural phenomenon.
"We may not know yet what's going on around this star," Marengo observed. "But that's what makes it so interesting."
Scientists first reported the findings in September, suggesting a family of comets as the most likely explanation. Other cited causes included fragments of planets and asteroids.
A new study using data from NASA's Spitzer Space Telescope addresses the mystery, finding more evidence for the scenario involving a swarm of comets. The study, led by Massimo Marengo of Iowa State University, Ames, is accepted for publication in the Astrophysical Journal Letters.
One way to learn more about the star is to study it in infrared light. Kepler had observed it in visible light. If a planetary impact, or a collision amongst asteroids, were behind the mystery of KIC 8462852, then there should be an excess of infrared light around the star. Dusty, ground-up bits of rock would be at the right temperature to glow at infrared wavelengths.
At first, researchers tried to look for infrared light using NASA's Wide-Field Infrared Survey Explorer, or WISE, and found none. But those observations were taken in 2010, before the strange events seen by Kepler -- and before any collisions would have kicked up dust.
To search for infrared light that might have been generated after the oddball events, researchers turned to Spitzer, which, like WISE, also detects infrared light. Spitzer just happened to observe KIC 8462852 more recently in 2015.
"Spitzer has observed all of the hundreds of thousands of stars where Kepler hunted for planets, in the hope of finding infrared emission from circumstellar dust," said Michael Werner, the Spitzer project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, and the lead investigator of that particular Spitzer/Kepler observing program.
But, like WISE, Spitzer did not find any significant excess of infrared light from warm dust. That makes theories of rocky smashups very unlikely, and favors the idea that cold comets are responsible. It's possible that a family of comets is traveling on a very long, eccentric orbit around the star. At the head of the pack would be a very large comet, which would have blocked the star's light in 2011, as noted by Kepler. Later, in 2013, the rest of the comet family, a band of varied fragments lagging behind, would have passed in front of the star and again blocked its light.
By the time Spitzer observed the star in 2015, those comets would be farther away, having continued on their long journey around the star. They would not leave any infrared signatures that could be detected.
According to Marengo, more observations are needed to help settle the case of KIC 8462852.
"This is a very strange star," he said. "It reminds me of when we first discovered pulsars. They were emitting odd signals nobody had ever seen before, and the first one discovered was named LGM-1 after 'Little Green Men.'"
In the end, the LGM-1 signals turned out to be a natural phenomenon.
"We may not know yet what's going on around this star," Marengo observed. "But that's what makes it so interesting."
Only 8% of the universe’s habitable worlds have formed so far
There are likely hundreds of millions of Earth-like planets in the Milky Way today, but that’s a small fraction of the number that may form throughout the universe in the future, a new study suggests. Using data from the Hubble Space Telescope, researchers estimated the rates of past star and planet formation in the universe, which is now about 13.8 billion years old. They then combined that information with data from previous surveys that estimated the amounts of hydrogen and helium left over from the big bang that still haven’t collapsed to form stars. At the time our solar system formed about 4.6 billion years ago, only about 39% of the hydrogen and helium in our galaxy had collapsed into clouds that then evolved into stars, they say. That means that the remaining 61% is available to form future solar systems that may include Earth-like planets in their habitable zones, the researchers report online today in Monthly Notices of the Royal Astronomical Society. In the universe as a whole, the researchers suggest, only 8% of its original starmaking gases was locked up in stars by Earth’s first birthday. The rest will, over the remaining trillions of years of the universe’s lifetime, coalesce into stars whose solar systems will contain a myriad of Earth-like planets (artist’s representations above).
Dying sun caught tearing apart its own asteroids (Science)
The Kepler Space Telescope has detected disintegrating asteroids orbiting a white dwarf, the type of burned-out star our sun will become about 8 billion years from now. The discovery explains why some white dwarfs have heavy elements on their surfaces and also gives us a possible preview of Earth's grisly fate.
"It's really amazing," says Jay Holberg, an astronomer at the University of Arizona in Tucson, who was not involved in the discovery. "We've never seen this before for a white dwarf."
A typical white dwarf is nearly as massive as the sun but only slightly larger than Earth, so the star exerts a strong gravitational pull at its surface: Drop a rock from a height of 1 meter and it would hit the star at thousands of kilometers per hour. The strong gravitational force should also yank all elements heavier than helium beneath the star's surface, yet the surfaces of many white dwarfs nevertheless possess heavy elements, suggesting that asteroids deposit elements such as silicon and iron.
Now, for the first time, researchers have seen this scenario unfold. Andrew Vanderburg, an astronomer at the Harvard-Smithsonian Center for Astrophysics, was analyzing data from Kepler, which detects planets when they block the light of their sun. "One of the white dwarfs suddenly popped up with this really intriguing signature," Vanderburg says. As his team reports online today in Nature, the white dwarf, located in the constellation Virgo and named WD 1145+017, has at least one, and probably several, asteroids that are disintegrating. As a debris cloud from each asteroid passes between us and the star, Kepler detects a dimming of the star's light.
"It's fascinating," says astronomer Michael Jura of the University of California, Los Angeles, who was not part of the discovery team. "They've actually caught in the act the process of some asteroid breaking into pieces, being disrupted by the white dwarf host star."
Indeed, the star itself is the asteroids' enemy. Its gravity has torn them asunder, and its light is vaporizing their rock. The asteroids are so close to the star that they revolve in just 4.5 to 4.9 hours; Vanderburg estimates they are roughly the size of Ceres, the largest asteroid between the orbits of Mars and Jupiter.
Billions of years from now, our sun will expand into a red giant, engulfing and incinerating Mercury and possibly Venus and Earth. Then the red sun will eject its outer layers and expose its hot core, which will contract into a white dwarf. Even if the sun never engulfs Earth, the drama may destabilize orbits in the solar system so that asteroids crash into our world and grind it up. Thus, the newly discovered asteroids could conceivably be the wreckage of a planet that once resembled our own.
"It's really amazing," says Jay Holberg, an astronomer at the University of Arizona in Tucson, who was not involved in the discovery. "We've never seen this before for a white dwarf."
A typical white dwarf is nearly as massive as the sun but only slightly larger than Earth, so the star exerts a strong gravitational pull at its surface: Drop a rock from a height of 1 meter and it would hit the star at thousands of kilometers per hour. The strong gravitational force should also yank all elements heavier than helium beneath the star's surface, yet the surfaces of many white dwarfs nevertheless possess heavy elements, suggesting that asteroids deposit elements such as silicon and iron.
Now, for the first time, researchers have seen this scenario unfold. Andrew Vanderburg, an astronomer at the Harvard-Smithsonian Center for Astrophysics, was analyzing data from Kepler, which detects planets when they block the light of their sun. "One of the white dwarfs suddenly popped up with this really intriguing signature," Vanderburg says. As his team reports online today in Nature, the white dwarf, located in the constellation Virgo and named WD 1145+017, has at least one, and probably several, asteroids that are disintegrating. As a debris cloud from each asteroid passes between us and the star, Kepler detects a dimming of the star's light.
"It's fascinating," says astronomer Michael Jura of the University of California, Los Angeles, who was not part of the discovery team. "They've actually caught in the act the process of some asteroid breaking into pieces, being disrupted by the white dwarf host star."
Indeed, the star itself is the asteroids' enemy. Its gravity has torn them asunder, and its light is vaporizing their rock. The asteroids are so close to the star that they revolve in just 4.5 to 4.9 hours; Vanderburg estimates they are roughly the size of Ceres, the largest asteroid between the orbits of Mars and Jupiter.
Billions of years from now, our sun will expand into a red giant, engulfing and incinerating Mercury and possibly Venus and Earth. Then the red sun will eject its outer layers and expose its hot core, which will contract into a white dwarf. Even if the sun never engulfs Earth, the drama may destabilize orbits in the solar system so that asteroids crash into our world and grind it up. Thus, the newly discovered asteroids could conceivably be the wreckage of a planet that once resembled our own.
Explore the Milky Way at 46 billion pixels
There is a whole lot of space out there beyond the Kármán line, and a lot of telescopes taking photos day after day and year after year. While we do get to see the most gorgeous of these images, showing interesting nebulas and other cosmic features, a great many more go unknown and unremarked beyond the research sphere.
But that doesn't mean they're useless. Far from it. For example, photographs taken by the Ruhr University Bochum's observatory in Chile's Atacama Desert have been the subject of intense scrutiny for the past five years under the leadership of Rolf Chini. The team has been scouring the Milky Way galaxy looking for objects of variable brightness that glow and dim.
They have been looking at a section of the southern sky so large that it needed to be divided into 268 sections, with each section photographed in intervals of several days. It is these 268 sections of photos that the team has stitched together into a massive mosaic of the Milky Way. At 46 billion pixels and a file size of 194 GB, it's the largest image of space ever created.
Last year, NASA released a 20 billion-pixel image of the Milky Way, compiled from over 2 million images. At the time, Spitzer Space Science Center imaging specialist Robert Hurt said that, if printed out, it would need a billboard the size of the Rose Bowl. This image is more than twice that size.
The mosaic has been uploaded to an interactive online tool, where anyone can zoom in and scroll around. A coordinates field in the lower left of the screen also acts as a text entry box to search for objects by coordinates, name, or catalogue number. You can also use a pop-up box in the upper left to apply various filters.
You may notice that the colours seem positively subdued compared to the space photos we are used to seeing. This is because the photos have been taken with a narrowband filter that doesn't let other colours through. This allows the team to get a more accurate reading of light variables.
So far, the Chair of Astrophysics' team has discovered over 50,000 new variable objects. These will be included in a catalogue being compiled by Moritz Hackstein for his PhD thesis.
You can have a go of the interactive tool here. Because it's so large, it tends to run a little on the slow side, but it's awe-inspiring nevertheless.
But that doesn't mean they're useless. Far from it. For example, photographs taken by the Ruhr University Bochum's observatory in Chile's Atacama Desert have been the subject of intense scrutiny for the past five years under the leadership of Rolf Chini. The team has been scouring the Milky Way galaxy looking for objects of variable brightness that glow and dim.
They have been looking at a section of the southern sky so large that it needed to be divided into 268 sections, with each section photographed in intervals of several days. It is these 268 sections of photos that the team has stitched together into a massive mosaic of the Milky Way. At 46 billion pixels and a file size of 194 GB, it's the largest image of space ever created.
Last year, NASA released a 20 billion-pixel image of the Milky Way, compiled from over 2 million images. At the time, Spitzer Space Science Center imaging specialist Robert Hurt said that, if printed out, it would need a billboard the size of the Rose Bowl. This image is more than twice that size.
The mosaic has been uploaded to an interactive online tool, where anyone can zoom in and scroll around. A coordinates field in the lower left of the screen also acts as a text entry box to search for objects by coordinates, name, or catalogue number. You can also use a pop-up box in the upper left to apply various filters.
You may notice that the colours seem positively subdued compared to the space photos we are used to seeing. This is because the photos have been taken with a narrowband filter that doesn't let other colours through. This allows the team to get a more accurate reading of light variables.
So far, the Chair of Astrophysics' team has discovered over 50,000 new variable objects. These will be included in a catalogue being compiled by Moritz Hackstein for his PhD thesis.
You can have a go of the interactive tool here. Because it's so large, it tends to run a little on the slow side, but it's awe-inspiring nevertheless.
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