In a far-off galaxy, 12.4 billion light-years from Earth, a ravenous black hole is devouring galactic grub. Its feeding frenzy produces so much energy, it stirs up gas across its entire galaxy.
"It is like a pot of boiling water being heated up by a nuclear reactor in the center," said Tanio Diaz-Santos of the Universidad Diego Portales in Santiago, Chile, lead author of a new study about this galaxy.
This galaxy, called W2246-0526, is the most luminous galaxy known, according to research published in 2015, based on data from NASA's Wide-field Infrared Survey Explorer (WISE). That means that it has the highest power output of any galaxy in the universe, and would appear to shine the brightest if all galaxies were at the same distance from us.
The new study, published in The Astrophysical Journal Letters, reveals that this galaxy is also expelling tremendously turbulent gas -- a phenomenon never seen before in an object of this kind.
"This galaxy is tearing itself apart," said Roberto Assef, astronomer with the Universidad Diego Portales and leader of the observing team at the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. "The momentum and energy of the particles of light deposited in the gas are so great that they are pushing the gas out in all directions."
Using ALMA, astronomers found large amounts of ionized carbon in a very turbulent state throughout the entire galaxy. The galaxy formed a little over 1 billion years after the big bang.
The growing supermassive black hole at the center of the galaxy is the likely engine of the turbulence. As the gravitational pull of the black hole attracts surrounding gas and other matter, the material forms a structure around it called an accretion disk. The friction from this disk produces the intense brightness, making the galaxy shine like a combination of more than 300 trillion suns.
The black hole's event horizon is thought to be one million times smaller than the W2246-0526 galaxy, yet the energy emitted by the black hole's swallowing of material affects gas thousands of light-years away from it.
While turbulence has been detected in gas around supermassive black holes before - for example, around the centers of some nearby luminous galaxies that host active galactic nuclei - those winds are found to flow in specific directions. This is the first time that highly turbulent gas has been found across the entire galaxy.
"The 'boiling' gas is not in the accretion disk. The whole galaxy is being disturbed," said Peter Eisenhardt, project scientist for WISE, based at NASA's Jet Propulsion Laboratory, Pasadena, California.
Researchers are unsure whether the gas is being pushed out strongly enough to leave the galaxy entirely, or if it will eventually fall back.
"A likely finale would be that the galaxy will blow out all of the gas and dust that is surrounding it, and we would see the accretion disk without its dust cover -- what we call a quasar," Assef said.
This galaxy is an example of a rare class of objects called Hot, Dust-Obscured Galaxies or Hot DOGs, which are powerful galaxies with supermassive black holes in their centers. Only 1 out of every 3,000 galaxies that WISE has observed is in this category.
The WISE mission was essential to finding this galaxy because the galaxy is covered in dust, obscuring its light from visible-wavelength telescopes. The dust shifts the light from the galaxy into the infrared range, to which WISE is attuned.
JPL managed and operated WISE for NASA's Science Mission Directorate in Washington. The spacecraft was put into hibernation mode in 2011, after it scanned the entire sky twice, thereby completing its main objectives. In September 2013, WISE was reactivated, renamed NEOWISE and assigned a new mission to assist NASA's efforts to identify potentially hazardous near-Earth objects.
Thursday 24 March 2016
Traces of the First Stars in the Universe Possibly Found
An enormous cloud of dust and gas may bear the fingerprints of the first stars in the universe. The distant cloud contains only a tiny amount of relatively heavy elements, which are manufactured in the hearts of stars, suggesting that these traces may have come from some of the first stars that ever existed. "The reason why we care [about the first stars] is intricately related with the air we're breathing right now," study co-author John O'Meara, of Saint Michael's College in Vermont, said last week at a press conference at the 227th Meeting of the American Astronomical Society in Kissimmee, Florida. "Early on in the universe, we didn't have those heavy elements [such as oxygen] at all."
Traces of the past
The universe's first stars were built primarily out of hydrogen and helium, the dominant elements that existed shortly after the Big Bang.
Fusion transformed the material at these stars' hearts into heavier elements, which were then blasted into space when the stars died in violent supernova explosions. Subsequent generations of stars incorporated this material into their bodies, building even heavier elements in their cores.
"It's clear the history of the universe is very much the history of the increase in the relative amounts of heavy elements over time," said O'Meara, who worked with study lead author Neil Crighton, as well as Michael Murphy, both of whom are based at Swinburne University of Technology
in Australia.The study team used the European Southern Observatory's Very Large Telescope (VLT) in Chile to study an ancient gas cloud as it appeared only 1.8 billion years after the Big Bang, which created the universe about 13.8 billion years ago.
As light from an extremely bright background object known as a quasar streamed through the cloud, the astronomers were able to determine the composition of its constituent gas. They found that the ancient cloud contained an extremely small percentage of heavy elements — traces that may have been scattered by the first generation of stars.
Previous surveys have revealed clouds of hydrogen and helium gas, but they were pristine, untouched by the heavy elements built within stars. This ancient gas cloud contains the smallest measurable traces of heavy elements ever found, the researchers said.
"It is the lowest amount of heavy elements ever determined in a gas cloud like this," O'Meara said.
'Down in the weeds'
The problem with studying massive clouds of gas in the early universe isn't that they are rare; it's that they are extremely common. The light from a single quasar can pierce through multiple clouds as it streams toward Earth. According to O'Meara, this can "muddle" the process of distinguishing heavy elements, because the signals are overlapping. "It was our willingness to go down in the weeds, to try to find those very rare systems where you could make that measurement" that made the observations possible, he said. Other such heavy-element-tinged clouds may exist as well, but scientists need to pore over a number of observations to find alignments where the signals can be precisely measured. "It's not to say they're not out there in abundance," O'Meara said. "The problem is just getting lucky." As instruments like NASA's $8.8 billion James Webb Space Telescope (JWST) come online in the near future, the hunt for such gas clouds might become easier. Rather than being limited to quasars, which are relatively few in number, scientists should be able to use galaxies as their background light source. "Once you can start using galaxies as a background source, you go from hundreds of thousands of objects on the sky to tens of millions," O'Meara said. Searching the universe for signs of these clouds today will help narrow down the list of potential targets for JWST in the future, he added. - See more at: http://www.space.com/31597-universe-first-stars-gas-cloud-evidence.html?cmpid=NL_SP_weekly_2016-1-13#sthash.FldSV4ca.dpuf
Exposed Water Ice on Comet Reveals Clues About Its Evolution - See more at: http://www.space.com/31607-water-ice-comet-rosetta-mission.html?cmpid=NL_SP_weekly_2016-1-13#sthash.wi0CUq4Z.dpuf
The European Space Agency's Rosetta spacecraft detected relatively large grains of water ice in two different places on the surface of Comet 67P/Churyumov-Gerasimenko, which the probe has been orbiting since August 2014.
These big grains may have formed after heat from the sun sublimated (or vaporized) buried water ice, which then recondensed and was redeposited in subsurface layers, without ever leaving Comet 67P, researchers said.
"If the thin ice-rich layers that we see exposed close to the surface are the result of the comet's activity, then they represent its evolution, and it does not necessarily require global layering to have occurred early in the comet's formation history," study lead author Gianrico Filacchione, of the Institute for Space Astrophysics and Planetology at the National Institute for Astrophysics in Rome, told Space.com via email.
Comets are made primarily of water ice, but the stuff is rarely observed on their frigid surfaces. Indeed, the 2.5-mile-wide (4 kilometers) Comet 67P appears to be covered by a nearly uniform layer of dark dust, Filacchione said.
"We have measured that the surface reflects only a few percent of solar light," he said. "Ices are not stable for a long time on the surface of the nucleus because, during the perihelion passage [closest approach to the sun], they sublimate, originating the gaseous coma."
Filacchione and his colleagues studied observations of Comet 67P made by Rosetta's Visual and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument. VIRTIS detected surface water ice in two separate, 3.3-foot-wide (1 meter) areas within a region of the comet dubbed Imhotep, the researchers report in a study published online today (Jan. 13) in the journal Nature.
It’s possible, Comerford says, that somehow during the turmoil of the merger millions of years ago, gravity could have stripped the smaller black hole of its stars. But perhaps it just started out with fewer stars because it’s a different sort of black hole. (The Chandra observations don’t reveal the objects’ masses.)
Although supermassive black holes—which can weigh up to billions of times the mass of our sun—dominate galactic centers, galaxies also contain many smaller black holes, most weighing several times—or several tens of times—the sun’s mass. Theorists predict that there must be an intermediate class weighing between 100 and 1 million solar masses, but so far there is little firm evidence for their existence. Astronomers can see objects that could be intermediate mass black holes—something they call ultraluminous x-ray sources—but the problem is that “Chandra doesn’t tell us what they are,” says Eric Schlegel of the University of Texas, San Antonio, who is not involved in the study.
Comerford suggests that the beauty mark in SDSS J1126+2944 is something different: the central black hole of a dwarf galaxy, typically a hundredth of the size of a normal galaxy. If SDSS J1126+2944 is the result of the merger of a normal-sized galaxy with a dwarf galaxy, this could explain the naked black hole in the Chandra images.
It’s not an accepted fact that dwarf galaxies have intermediate black holes at their hearts. Although Schlegel says that SDSS J1126+2944 does look like the result of a merger, and so Comerford’s team isn’t seeing an ultraluminous x-ray source, he says it’s too early to discount the possibility that it’s just a normal supermassive black hole that got stripped. “When you collide these things [galaxies], stuff goes everywhere.”
Astronomers are finding dozens of the fastest stars in our galaxy with the help of images from NASA's Spitzer Space Telescope and Wide-field Infrared Survey Explorer, or WISE.
When some speedy, massive stars plow through space, they can cause material to stack up in front of them in the same way that water piles up ahead of a ship. Called bow shocks, these dramatic, arc-shaped features in space are leading researchers to uncover massive, so-called runaway stars.
"Some stars get the boot when their companion star explodes in a supernova, and others can get kicked out of crowded star clusters," said astronomer William Chick from the University of Wyoming in Laramie, who presented his team's new results at the American Astronomical Society meeting in Kissimmee, Florida. "The gravitational boost increases a star's speed relative to other stars."
Our own sun is strolling through our Milky Way galaxy at a moderate pace. It is not clear whether our sun creates a bow shock. By comparison, a massive star with a stunning bow shock, called Zeta Ophiuchi (or Zeta Oph), is traveling around the galaxy faster than our sun, at 54,000 mph (24 kilometers per second) relative to its surroundings. Zeta Oph's giant bow shock can be seen in this image from the WISE mission:
http://www.nasa.gov/mission_pages/WISE/multimedia/gallery/pia13455.html
Both the speed of stars moving through space and their mass contribute to the size and shapes of bow shocks. The more massive a star, the more material it sheds in high-speed winds. Zeta Oph, which is about 20 times as massive as our sun, has supersonic winds that slam into the material in front of it.
The result is a pile-up of material that glows. The arc-shaped material heats up and shines with infrared light. That infrared light is assigned the color red in the many pictures of bow shocks captured by Spitzer and WISE.
Chick and his team turned to archival infrared data from Spitzer and WISE to identify new bow shocks, including more distant ones that are harder to find. Their initial search turned up more than 200 images of fuzzy red arcs. They then used the Wyoming Infrared Observatory, near Laramie, to follow up on 80 of these candidates and identify the sources behind the suspected bow shocks. Most turned out to be massive stars.
The findings suggest that many of the bow shocks are the result of speedy runaways that were given a gravitational kick by other stars. However, in a few cases, the arc-shaped features could turn out to be something else, such as dust from stars and birth clouds of newborn stars. The team plans more observations to confirm the presence of bow shocks.
"We are using the bow shocks to find massive and/or runaway stars," said astronomer Henry "Chip" Kobulnicky, also from the University of Wyoming. "The bow shocks are new laboratories for studying massive stars and answering questions about the fate and evolution of these stars."
Another group of researchers, led by Cintia Peri of the Argentine Institute of Radio Astronomy, is also using Spitzer and WISE data to find new bow shocks in space. Only instead of searching for the arcs at the onset, they start by hunting down known speedy stars, and then they scan them for bow shocks.
"WISE and Spitzer have given us the best images of bow shocks so far," said Peri. "In many cases, bow shocks that looked very diffuse before, can now be resolved, and, moreover, we can see some new details of the structures."
Some of the first bow shocks from runaway stars were identified in the 1980s by David Van Buren of NASA's Jet Propulsion Laboratory in Pasadena, California. He and his colleagues found them using infrared data from the Infrared Astronomical Satellite (IRAS), a predecessor to WISE that scanned the whole infrared sky in 1983.
Wednesday 23 March 2016
Moon Mystery Solved! Apollo Rocket Impact Site Finally Found
The S-IVB was the third stage of NASA's huge Saturn V rocket, which blasted the Apollo astronauts to the moon. Beginning with the Apollo 13 mission in 1970, S-IVBs were sent to impact the lunar surface. Earlier Apollo missions had placed seismometers on the moon, allowing scientists to study the object's interior structure when the leftover rocket stages hit.
The S-IVBs' impact sites were estimated from old tracking data. LRO, which has been circling the moon since 2009, had previously found the spots where the booster stages used with the Apollo 13, 14, 15 and 17 missions had landed.
But nobody was quite sure where Apollo 16's S-IVB fell, because contact with the stage was lost for a short time when it was on its way down. As it happened, the actual impact site was off by about 19 miles (30 km) from the place where tracking systems of the day predicted it would be, LROC team members said.
Two images showing the impact site of the Apollo 16 mission's S-IVB rocket stage, which hit the lunar surface in April 1972. Each image shows a swathe of the moon 1,300 feet (400 meters) wide; north is up.
Two images showing the impact site of the Apollo 16 mission's S-IVB rocket stage, which hit the lunar surface in April 1972. Each image shows a swathe of the moon 1,300 feet (400 meters) wide; north is up.
Craters caused by S-IVB crashes are much shallower than the holes gouged out by asteroids and comets.
"The craters from the booster impacts are unusual because they are formed by very low-density projectiles traveling at relatively low velocity (2.6 km per second; 5,800 mph)," LROC team members wrote in a description of the Apollo 16 S-IVB discovery images.
"The S-IVB booster can be imagined as an empty soda can hitting the surface — just an outer metal shell with very little interior mass (all of the fuel was used to send the astronauts toward the moon and the tanks were empty)," they added. "During the impact, much of the energy went into crushing the booster, and only a shallow crater was formed."
Physicists figure out how to retrieve information from a black hole
Black holes earn their name because their gravity is so strong not even light can escape from them. Oddly, though, physicists have come up with a bit of theoretical sleight of hand to retrieve a speck of information that's been dropped into a black hole. The calculation touches on one of the biggest mysteries in physics: how all of the information trapped in a black hole leaks out as the black hole "evaporates." Many theorists think that must happen, but they don't know how.
Unfortunately for them, the new scheme may do more to underscore the difficulty of the larger "black hole information problem" than to solve it. "Maybe others will be able to go further with this, but it's not obvious to me that it will help," says Don Page, a theorist at the University of Alberta in Edmonton, Canada, who was not involved in the work.
You can shred your tax returns, but you shouldn't be able to destroy information by tossing it into a black hole. That's because, even though quantum mechanics deals in probabilities—such as the likelihood of an electron being in one location or another—the quantum waves that give those probabilities must still evolve predictably, so that if you know a wave's shape at one moment you can predict it exactly at any future time. Without such "unitarity" quantum theory would produce nonsensical results such as probabilities that don't add up to 100%.
But suppose you toss some quantum particles into a black hole. At first blush, the particles and the information they encode is lost. That's a problem, as now part of the quantum state describing the combined black hole-particles system has been obliterated, making it impossible to predict its exact evolution and violating unitarity.
Physicists think they have a way out. In 1974, British theorist Stephen Hawking argued that black holes can radiate particles and energy. Thanks to quantum uncertainty, empty space roils with pairs of particles flitting in and out of existence. Hawking realized that if a pair of particles from the vacuum popped into existence straddling the black hole's boundary then one particle could fly into space, while the other would fall into the black hole. Carrying away energy from the black hole, the exiting Hawking radiation should cause a black hole to slowly evaporate. Some theorists suspect information reemerges from the black hole encoded in the radiation—although how remains unclear as the radiation is supposedly random.
Now, Aidan Chatwin-Davies, Adam Jermyn, and Sean Carroll of the California Institute of Technology in Pasadena have found an explicit way to retrieve information from one quantum particle lost in a black hole, using Hawking radiation and the weird concept of quantum teleportation.
Quantum teleportation enables two partners, Alice and Bob, to transfer the delicate quantum state of one particle such as an electron to another. In quantum theory, an electron can spin one way (up), the other way (down), or literally both ways at once. In fact, its state can be described by a point on a globe in which north pole signifies up and the south pole signifies down. Lines of latitude denote different mixtures of up and down, and lines of longitude denote the "phase," or how the up and down parts mesh. However, if Alice tries to measure that state, it will "collapse" one way or the other, up or down, squashing information such as the phase. So she can't measure the state and send the information to Bob, but must transfer it intact.
To do that Alice and Bob can share an additional pair of electrons connected by a special quantum link called entanglement. The state of either particle in the entangled pair is uncertain—it simultaneously points everywhere on the globe—but the states are correlated so that if Alice measures her particle from the pair and finds it spinning, say, up, she'll know instantly that Bob's electron is spinning down. So Alice has two electrons—the one whose state she wants to teleport and her half of the entangled pair. Bob has just the one from the entangled pair.
To perform the teleportation, Alice takes advantage of one more strange property of quantum mechanics: that measurement not only reveals something about a system, it also changes its state. So Alice takes her two unentangled electrons and performs a measurement that "projects" them into an entangled state. That measurement breaks the entanglement between the pair of electrons that she and Bob share. But at the same time, it forces Bob's electron into the state that her to-be-teleported electron was in. It's as if, with the right measurement, Alice squeezes the quantum information from one side of the system to the other.
Chatwin-Davies and colleagues realized that they could teleport the information about the state of an electron out of a black hole, too. Suppose that Alice is floating outside the black hole with her electron. She captures one photon from a pair born from Hawking radiation. Much like an electron, the photon can spin in either of two directions, and it will be entangled with its partner photon that has fallen into the black hole. Next, Alice measures the total angular momentum, or spin, of the black hole—both its magnitude and, roughly speaking, how much it lines up with a particular axis. With those two bits of information in hand, she then tosses in her electron, losing it forever.
But Alice can still recover the information about the state of that electron, the team reports in a paper in press at Physical Review Letters. All she has to do is once again measure the spin and orientation of the black hole. Those measurements then entangle the black hole and the in-falling photon. They also teleport the state of the electron to the photon that Alice captured. Thus, the information from the lost electron is dragged back into the observable universe.
Chatwin-Davies stresses that the scheme is not a plan for a practical experiment. After all, it would require Alice to almost instantly measure the spin of a black hole as massive as the sun to within a single atom's spin. "We like to joke around that Alice is the most advanced scientist in the universe," he says.
The scheme also has major limitations. In particular, as the authors note, it works for one quantum particle, but not for two or more. That's because the recipe exploits the fact that the black hole conserves angular momentum, so that its final spin is equal to its initial spin plus that of the electron. That trick enables Alice to get out exactly two bits of information—the total spin and its projection along one axis—and that's just enough information to specify the latitude and longitude of quantum state of one particle. But it's not nearly enough to recapture all the information trapped in a black hole, which typically forms when a star collapses upon itself.
To really tackle the black hole information problem, theorists would also have to account for the complex states of the black hole's interior, says Stefan Leichenauer, a theorist at the University of California, Berkeley. "Unfortunately, all of the big questions we have about black holes are precisely about these internal workings," he says. "So, this protocol, though interesting in its own right, will probably not teach us much about the black hole information problem in general."
However, delving into the interior of black holes would require a quantum mechanical theory of gravity. Of course, developing such a theory is perhaps the grandest goal in all of theoretical physics, one that has eluded physicists for decades.
Unfortunately for them, the new scheme may do more to underscore the difficulty of the larger "black hole information problem" than to solve it. "Maybe others will be able to go further with this, but it's not obvious to me that it will help," says Don Page, a theorist at the University of Alberta in Edmonton, Canada, who was not involved in the work.
You can shred your tax returns, but you shouldn't be able to destroy information by tossing it into a black hole. That's because, even though quantum mechanics deals in probabilities—such as the likelihood of an electron being in one location or another—the quantum waves that give those probabilities must still evolve predictably, so that if you know a wave's shape at one moment you can predict it exactly at any future time. Without such "unitarity" quantum theory would produce nonsensical results such as probabilities that don't add up to 100%.
But suppose you toss some quantum particles into a black hole. At first blush, the particles and the information they encode is lost. That's a problem, as now part of the quantum state describing the combined black hole-particles system has been obliterated, making it impossible to predict its exact evolution and violating unitarity.
Physicists think they have a way out. In 1974, British theorist Stephen Hawking argued that black holes can radiate particles and energy. Thanks to quantum uncertainty, empty space roils with pairs of particles flitting in and out of existence. Hawking realized that if a pair of particles from the vacuum popped into existence straddling the black hole's boundary then one particle could fly into space, while the other would fall into the black hole. Carrying away energy from the black hole, the exiting Hawking radiation should cause a black hole to slowly evaporate. Some theorists suspect information reemerges from the black hole encoded in the radiation—although how remains unclear as the radiation is supposedly random.
Now, Aidan Chatwin-Davies, Adam Jermyn, and Sean Carroll of the California Institute of Technology in Pasadena have found an explicit way to retrieve information from one quantum particle lost in a black hole, using Hawking radiation and the weird concept of quantum teleportation.
Quantum teleportation enables two partners, Alice and Bob, to transfer the delicate quantum state of one particle such as an electron to another. In quantum theory, an electron can spin one way (up), the other way (down), or literally both ways at once. In fact, its state can be described by a point on a globe in which north pole signifies up and the south pole signifies down. Lines of latitude denote different mixtures of up and down, and lines of longitude denote the "phase," or how the up and down parts mesh. However, if Alice tries to measure that state, it will "collapse" one way or the other, up or down, squashing information such as the phase. So she can't measure the state and send the information to Bob, but must transfer it intact.
To do that Alice and Bob can share an additional pair of electrons connected by a special quantum link called entanglement. The state of either particle in the entangled pair is uncertain—it simultaneously points everywhere on the globe—but the states are correlated so that if Alice measures her particle from the pair and finds it spinning, say, up, she'll know instantly that Bob's electron is spinning down. So Alice has two electrons—the one whose state she wants to teleport and her half of the entangled pair. Bob has just the one from the entangled pair.
To perform the teleportation, Alice takes advantage of one more strange property of quantum mechanics: that measurement not only reveals something about a system, it also changes its state. So Alice takes her two unentangled electrons and performs a measurement that "projects" them into an entangled state. That measurement breaks the entanglement between the pair of electrons that she and Bob share. But at the same time, it forces Bob's electron into the state that her to-be-teleported electron was in. It's as if, with the right measurement, Alice squeezes the quantum information from one side of the system to the other.
Chatwin-Davies and colleagues realized that they could teleport the information about the state of an electron out of a black hole, too. Suppose that Alice is floating outside the black hole with her electron. She captures one photon from a pair born from Hawking radiation. Much like an electron, the photon can spin in either of two directions, and it will be entangled with its partner photon that has fallen into the black hole. Next, Alice measures the total angular momentum, or spin, of the black hole—both its magnitude and, roughly speaking, how much it lines up with a particular axis. With those two bits of information in hand, she then tosses in her electron, losing it forever.
But Alice can still recover the information about the state of that electron, the team reports in a paper in press at Physical Review Letters. All she has to do is once again measure the spin and orientation of the black hole. Those measurements then entangle the black hole and the in-falling photon. They also teleport the state of the electron to the photon that Alice captured. Thus, the information from the lost electron is dragged back into the observable universe.
Chatwin-Davies stresses that the scheme is not a plan for a practical experiment. After all, it would require Alice to almost instantly measure the spin of a black hole as massive as the sun to within a single atom's spin. "We like to joke around that Alice is the most advanced scientist in the universe," he says.
The scheme also has major limitations. In particular, as the authors note, it works for one quantum particle, but not for two or more. That's because the recipe exploits the fact that the black hole conserves angular momentum, so that its final spin is equal to its initial spin plus that of the electron. That trick enables Alice to get out exactly two bits of information—the total spin and its projection along one axis—and that's just enough information to specify the latitude and longitude of quantum state of one particle. But it's not nearly enough to recapture all the information trapped in a black hole, which typically forms when a star collapses upon itself.
To really tackle the black hole information problem, theorists would also have to account for the complex states of the black hole's interior, says Stefan Leichenauer, a theorist at the University of California, Berkeley. "Unfortunately, all of the big questions we have about black holes are precisely about these internal workings," he says. "So, this protocol, though interesting in its own right, will probably not teach us much about the black hole information problem in general."
However, delving into the interior of black holes would require a quantum mechanical theory of gravity. Of course, developing such a theory is perhaps the grandest goal in all of theoretical physics, one that has eluded physicists for decades.
Galaxy Grows Monstrous X-Ray Tail
Using the X-ray vision of NASA’s Chandra space telescope, the ghostly glow of a 250,000 light-year long tail has been seen streaming from a galaxy called deep inside the Zwicky 8338 cluster nearly 700 million light-years from Earth. This tail, a stream of superheated interstellar gases, has been ripped from the galaxy as it interacts with the hotter intragalactic gases inside the cluster.
The temperature of the tail gases has been gauged at around 10 million degrees Kelvin (Celsius), whereas the intragalactic gases in Zwicky 8338 are 3 times hotter.
Of most interest is the gap between the tail and the galaxy, a possible indication that all the available star-forming gases inside the galaxy has been blown away and depleted.
“The large separation between the galaxy and the tail might be telling us that the gas has been completely stripped off the galaxy,” said Thomas Reiprich, University of Bonn in Germany. “In effect, the tail has been cut off from the galaxy.”
Astronomers speculate that the galaxy’s loss may be the cluster’s gain; this tail of gas, that extends over twice the width of our galaxy, could spawn an island of star formation all by itself. Infrared studies of CGCG254-021 have shown that there is very little active star formation underway, likely a symptom of the massive gas loss that formed the tail.
Other characteristics of the tail gases have been studied, including the higher concentration of heavier elements (than helium) in the “head” of the tail (the brighter, cooler blob nearest its parent galaxy). There’s also evidence of a bow shock leading the tail — both galaxy and tail are known to be traveling downward in this observation. The shock is generated by this supersonic motion through the cluster’s intragalactic medium.
“This tail is a vivid example of how dynamic galaxy clusters are, as we may be seeing the transformation of a galaxy as it moves through the cluster,” said Gerrit Schellenberger of the University of Bonn in Germany, who led the study that is published in the November edition of the journal Astronomy and Astrophysics. “Also, the material in the tail includes not only hydrogen but heavier elements, and could spawn a new generation of stars trailing behind the galaxy.”
Galaxy clusters are of huge interest as they are so massive. Often containing hundreds to thousands of individual galaxies, this vast structures are islands of intense gravitational dominance over space-time and known to be reservoirs of dark matter — the invisible stuff that makes up around 85 percent of all mass in the universe. By looking deep into these clusters we can better understand how individual galaxies evolve.
“Since galaxy clusters are so enormous, they play a critical role in understanding how our Universe evolves,” added Schellenberger. “To understand galaxy clusters we need to understand how their galaxies change with time, and these X-ray tails provide an important element.”
‘Hot Jupiters’ spotted forming close to their suns
Of the alien solar systems we’ve spotted, many seem to have one intriguing thing in common: giant gas planets like Jupiter and Saturn orbiting very close to their parent star. How did such “hot Jupiters” form? Did they coalesce farther out and migrate inward, or were they born in situ? Now, a team using the world’s largest radio telescope array has found evidence for a close-in formation. The Atacama Large Millimeter/Submillimeter Array (ALMA), high up in the deserts of northern Chile, is sensitive to light from cooler objects of the cosmos: clouds of gas and dust rather than burning stars. The team used it to look at the disks of material around young stars from which planets form. In particular they looked at four “transitional disks,” which appear to have no dust close in to the star. Was it blown outward by stellar wind and radiation, or swept up by a forming exoplanet? As the astronomers report today in Astronomy & Astrophysics, they used the extreme sensitivity of ALMA, whose 66 dishes act as one telescope and can be positioned up to 14 kilometers apart, to scrutinize those gaps around the stars. They found that the gap still contained a lot of gas (blue in the picture, and dust brown), but that gas also had a smaller gap close to the star. Such an arrangement can only be explained, they say, by a giant exoplanet (just left of the star)—which ALMA can’t see—sweeping up all the material close to the star but pushing dust farther out still. Theorists will have to refine their models of planet formation, but will still have to explain how systems like our own ended up with giant planets farther out and small planets in closer orbits.
Missing Water Mystery Solved in Comprehensive Survey of Exoplanets
A survey of 10 hot, Jupiter-sized exoplanets conducted with NASA's Hubble and Spitzer space telescopes has led a team to solve a long-standing mystery -- why some of these worlds seem to have less water than expected. The findings offer new insights into the wide range of planetary atmospheres in our galaxy and how planets are assembled.
Of the nearly 2,000 planets confirmed to be orbiting other stars, a subset of them are gaseous planets with characteristics similar to those of Jupiter. However, they orbit very close to their stars, making them blistering hot.
Their close proximity to the star makes them difficult to observe in the glare of starlight. Due to this difficulty, Hubble has only explored a handful of hot Jupiters in the past. These initial studies have found several planets to hold less water than predicted by atmospheric models.
The international team of astronomers has tackled the problem by making the largest-ever spectroscopic catalogue of exoplanet atmospheres. All of the planets in the catalog follow orbits oriented so the planet passes in front of their parent star, as seen from Earth. During this so-called transit, some of the starlight travels through the planet's outer atmosphere. "The atmosphere leaves its unique fingerprint on the starlight, which we can study when the light reaches us," explains co-author Hannah Wakeford, now at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
By combining data from NASA's Hubble and Spitzer Space Telescopes, the team was able to attain a broad spectrum of light covering wavelengths from optical to infrared. The difference in planetary radius as measured between visible and infrared wavelengths was used to indicate the type of planetary atmosphere being observed for each planet in the sample, whether hazy or clear. A cloudy planet will appear larger in visible light than at infrared wavelengths, which penetrate deeper into the atmosphere. It was this comparison that allowed the team to find a correlation between hazy or cloudy atmospheres and faint water detection.
"I'm really excited to finally see the data from this wide group of planets together, as this is the first time we've had sufficient wavelength coverage to compare multiple features from one planet to another," says David Sing of the University of Exeter, U.K., lead author of the paper. "We found the planetary atmospheres to be much more diverse than we expected."
"Our results suggest it's simply clouds hiding the water from prying eyes, and therefore rule out dry hot Jupiters," explained co-author Jonathan Fortney of the University of California, Santa Cruz. "The alternative theory to this is that planets form in an environment deprived of water, but this would require us to completely rethink our current theories of how planets are born."
The results are being published in the December 14 issue of the British science journal Nature.
The study of exoplanetary atmospheres is currently in its infancy. Hubble's successor, the James Webb Space Telescope, will open a new infrared window on the study of exoplanets and their atmospheres.
Physicists find new evidence for helium ‘rain’ on Saturn
Using one of the world’s most powerful lasers, physicists have found experimental evidence for Saturn’s helium “rain,” a phenomenon in which a mixture of liquid hydrogen and helium separates like oil and water, sending droplets of helium deep in the planet’s atmosphere. The results show the range of blistering temperatures and crushing pressures at which this takes place. But they also suggest that a helium rain could also fall on Jupiter, where such behavior was almost completely unexpected.
“We’re showing the first experimental evidence at conditions relevant to Jupiter and Saturn,” says Gilbert Collins, an extreme matter physicist at Lawrence Livermore National Laboratory (LLNL) in Livermore, California. “It’s a surprise that [this] happens over such a broad regime of temperatures and densities.” Collins described the results in a talk yesterday at a meeting of the American Geophysical Union in San Francisco, California.
Saturn is more than 50% brighter than it ought to be for a normally cooling planet. One way to account for this is through the behavior of its massive envelope of hydrogen and helium gases. As temperatures and pressures rise in the planet’s interior, the gases become liquids. At still deeper levels, the liquid hydrogen becomes electrically conductive, or metallic, while the liquid helium remains mixed in. But once conditions surpass a certain threshold of pressures and temperatures, the liquid helium is expected to fall out of the dissolved mixture. According to theory, this liquid helium forms droplets of “rain” that fall farther towards Saturn’s core, unleashing gravitational potential energy that makes Saturn more luminous.
Theorists imagined this could never happen on Jupiter, which is hotter than Saturn. This extra heat is thought to stir up the helium-hydrogen mixtures more vigorously, preventing the helium from falling out as rain. Theories have suggested helium rain on Saturn since the mid-1970s, but experimental evidence has been lacking.
The evidence is now in. Collins and his colleagues used the OMEGA laser at the Laboratory for Laser Energetics at the University of Rochester in New York, which can produce 40 kilojoule pulses of intense light for a nanosecond. They first put a hydrogen and helium mixture between two diamond crystals, compressing the mixture until it became a liquid. Then they shot the laser through one end of the diamond anvil cell—vaporizing the diamond instantly and sending in shock waves that further compressed the mixture. At certain temperature and pressure thresholds, the scientists noticed a sharp rise in the conductivity of the mixture—a sign that the helium had separated out of the soup and left only the highly conductive metallic hydrogen.
“That’s what triggered us to think: There’s something going on here. It looks like something strange is happening with the conductivity,” says Marius Millot, an LLNL physicist and member of the team. Millot says it took about 5 years and 300 laser shots to sketch out the phase transition across temperatures between 3000 and 20,000 kelvins and pressures between 30 and 300 gigapascals. They found that the separation occurred far more often than they expected—even at temperatures and pressures that would be found on Jupiter, he says. “People were thinking it was just in Saturn,” he says. “What we found is that maybe in both planets it occurs. The evolution of these planets may have been dramatically influenced by this separation.”
The results are “unexpected” and “exciting,” says Sarah Stewart, a planetary scientist at the University of California, Davis, who was not involved in the study. Although the experimental confirmation of helium rain on Saturn is reassuring, she says, the fact that it may happen on Jupiter creates a thorny problem for theorists. “It certainly makes everyone nervous,” she says. “If it messes up Jupiter, we don’t have a complete model for the evolution of the giant planets.”
But OMEGA’s results may not be the final word. Its measurements often conflict with those of Sandia National Laboratory’s Z machine, which can perform similar high-pressure experiments. “It’s a reflection of how hard it is to do experiments in this range,” says Stewart, who adds she will be looking to the Z machine for confirmation of the new results.
David Stevenson, a planetary scientist at the California Institute of Technology in Pasadena and one of the theorists who originally proposed the mechanism of helium rain, said in an email that it’s always good to get experimental confirmation of a theory. But the way in which the OMEGA results match his predictions from the 1970s so well, he jokes, “must be a coincidence.”
Stewart says the study should help NASA’s Juno mission come up with better models of Jupiter’s interior layers when the spacecraft goes into orbit around the planet in July 2016.
“We’re showing the first experimental evidence at conditions relevant to Jupiter and Saturn,” says Gilbert Collins, an extreme matter physicist at Lawrence Livermore National Laboratory (LLNL) in Livermore, California. “It’s a surprise that [this] happens over such a broad regime of temperatures and densities.” Collins described the results in a talk yesterday at a meeting of the American Geophysical Union in San Francisco, California.
Saturn is more than 50% brighter than it ought to be for a normally cooling planet. One way to account for this is through the behavior of its massive envelope of hydrogen and helium gases. As temperatures and pressures rise in the planet’s interior, the gases become liquids. At still deeper levels, the liquid hydrogen becomes electrically conductive, or metallic, while the liquid helium remains mixed in. But once conditions surpass a certain threshold of pressures and temperatures, the liquid helium is expected to fall out of the dissolved mixture. According to theory, this liquid helium forms droplets of “rain” that fall farther towards Saturn’s core, unleashing gravitational potential energy that makes Saturn more luminous.
Theorists imagined this could never happen on Jupiter, which is hotter than Saturn. This extra heat is thought to stir up the helium-hydrogen mixtures more vigorously, preventing the helium from falling out as rain. Theories have suggested helium rain on Saturn since the mid-1970s, but experimental evidence has been lacking.
The evidence is now in. Collins and his colleagues used the OMEGA laser at the Laboratory for Laser Energetics at the University of Rochester in New York, which can produce 40 kilojoule pulses of intense light for a nanosecond. They first put a hydrogen and helium mixture between two diamond crystals, compressing the mixture until it became a liquid. Then they shot the laser through one end of the diamond anvil cell—vaporizing the diamond instantly and sending in shock waves that further compressed the mixture. At certain temperature and pressure thresholds, the scientists noticed a sharp rise in the conductivity of the mixture—a sign that the helium had separated out of the soup and left only the highly conductive metallic hydrogen.
“That’s what triggered us to think: There’s something going on here. It looks like something strange is happening with the conductivity,” says Marius Millot, an LLNL physicist and member of the team. Millot says it took about 5 years and 300 laser shots to sketch out the phase transition across temperatures between 3000 and 20,000 kelvins and pressures between 30 and 300 gigapascals. They found that the separation occurred far more often than they expected—even at temperatures and pressures that would be found on Jupiter, he says. “People were thinking it was just in Saturn,” he says. “What we found is that maybe in both planets it occurs. The evolution of these planets may have been dramatically influenced by this separation.”
The results are “unexpected” and “exciting,” says Sarah Stewart, a planetary scientist at the University of California, Davis, who was not involved in the study. Although the experimental confirmation of helium rain on Saturn is reassuring, she says, the fact that it may happen on Jupiter creates a thorny problem for theorists. “It certainly makes everyone nervous,” she says. “If it messes up Jupiter, we don’t have a complete model for the evolution of the giant planets.”
But OMEGA’s results may not be the final word. Its measurements often conflict with those of Sandia National Laboratory’s Z machine, which can perform similar high-pressure experiments. “It’s a reflection of how hard it is to do experiments in this range,” says Stewart, who adds she will be looking to the Z machine for confirmation of the new results.
David Stevenson, a planetary scientist at the California Institute of Technology in Pasadena and one of the theorists who originally proposed the mechanism of helium rain, said in an email that it’s always good to get experimental confirmation of a theory. But the way in which the OMEGA results match his predictions from the 1970s so well, he jokes, “must be a coincidence.”
Stewart says the study should help NASA’s Juno mission come up with better models of Jupiter’s interior layers when the spacecraft goes into orbit around the planet in July 2016.
How to see a supernova twice
Finding a supernova—the huge explosion that marks the death of a star—in a distant galaxy is lucky enough, but one group of astronomers also got the bonus of an instant replay, thanks to gravity. The team first witnessed the supernova last year, as it exploded behind a massive cluster of galaxies 5 billion light-years from Earth called MACS J1149.5+2223. They noticed four images of the same supernova arranged around a galaxy in what is known as an “Einstein cross.” This lensing effect happens when the gravity of a galaxy bends the light of an object behind it so that, from Earth, we see four images of the same object. The team realized that other galaxies in the cluster might be gravitationally lensing light from the same supernova. But, as the light would follow different paths, it would take more or less time to reach Earth. So they set out to carefully model all the matter, conventional and dark, in the galaxy cluster to predict when and where lensed images of the supernova might appear (pictured). One appearance, they calculated, must have happened in 1998, but no telescopes were watching. Another one, they reckoned, was due to happen just about now. On 11 December, the Hubble Space Telescope struck oil: An image of the same supernova appeared just as predicted, the first time such an event has been successfully forecast. The sighting is also a powerful demonstration of astronomers’ ability to model the effect of gravitational mass on light.
Tiny Star Shoots Out Flares 10,000 Times Brighter Than the Sun's (Dec 2015 Space.com)
A small, cool star is emitting flares 10,000 times brighter than those ejected by the sun, a find that could be bad news for those hoping to find the galaxy filled with life.
The star's massive bursts of radiation, revealed in new research, could inhibit the evolution of life on planets orbiting the star, or at least severely disrupt it. If other stars of this type also have such intense flares, it could mean life in the universe is less likely to develop.
"If we lived around a star like this one, we wouldn't have any satellite communications," Peter Williams, of the Harvard-Smithsonian Center for Astrophysics (CfA), said in a statement. Williams leads a team of researchers in studying the star using the Atacama Large Millimeter/Submillimeter Array (ALMA), a massive radio telescope in Chile.
"In fact, it might be extremely difficult for life to evolve at all in such a stormy environment," Williams said in the statement.
"A very different beast"
Dim red dwarf stars dominate in the Milky Way, making up about three-fourths of the stellar population of the galaxy. The well-known star Williams targeted is a cool red dwarf, less than 1 percent as massive as the sun. It lies about 35 light-years from Earth, in the constellation Boites.
Previous studies of the star from the Karl G. Jansky Very Large Array in New Mexico revealed that the tiny star has a magnetic field several times stronger than the sun, although the physical processes that build the sun's magnetic field shouldn't work for such a small star.
"This star is a very different beast from our sun, magnetically speaking," CfA co-author Edo Berger said.
Williams and his team turned ALMA's powerful focus toward the tiny star, making the first detections of flarelike emissions from a red dwarf star at such high frequencies. The bursts of light created by the flares are 10,000 times brighter than those produced by the sun. Their presence in the short window of observations suggests that such flares are constantly being produced.
In their research, which has been accepted for publication in The Astrophysical Journal, the scientists named ALMA's extreme sensitivity as the key to detecting the flares. The measurement not only reveals more about the tiny star, but also opens the door to investigating other ultracool red dwarfs.
Bad news for life
If such emission is consistent across red dwarfs, it could mean bad news for the ability of life to evolve in the galaxy. Red dwarfs dominate the Milky Way, making up about three-fourths of all stars. Since NASA's Kepler telescope found planets around these worlds, the debate over whether or not they could host life has gone back and forth.
In order to hold liquid water on its surface, a condition necessary for life to evolve, a planet orbiting a dim red dwarf must lie significantly closer to its star than Earth lies to the sun. This region is known as the habitable zone. But its close proximity puts the planet at risk from stellar flares and coronal mass ejections, bursts of charged particles that stream out from a star. Stellar winds also carry charged particles away, potentially toward the planet.
If radiation reaches the surface of a planet, it can be damaging for any life growing there. Earth has a thick atmosphere that blocks most of the sun's rays, but the radiation that comes from orbiting very close to a red dwarf could tear away that type of protection. Plus, the extra-intense activity found around the ultracool red dwarf studied by Williams' team may make it even more challenging.
"It's like living in Tornado Alley in the U.S. Your location puts you at greater risk of severe storms," Williams said.
"A planet in the habitable zone of a star like this would be buffeted by storms much stronger than those generated by the sun."
The star's massive bursts of radiation, revealed in new research, could inhibit the evolution of life on planets orbiting the star, or at least severely disrupt it. If other stars of this type also have such intense flares, it could mean life in the universe is less likely to develop.
"If we lived around a star like this one, we wouldn't have any satellite communications," Peter Williams, of the Harvard-Smithsonian Center for Astrophysics (CfA), said in a statement. Williams leads a team of researchers in studying the star using the Atacama Large Millimeter/Submillimeter Array (ALMA), a massive radio telescope in Chile.
"In fact, it might be extremely difficult for life to evolve at all in such a stormy environment," Williams said in the statement.
"A very different beast"
Dim red dwarf stars dominate in the Milky Way, making up about three-fourths of the stellar population of the galaxy. The well-known star Williams targeted is a cool red dwarf, less than 1 percent as massive as the sun. It lies about 35 light-years from Earth, in the constellation Boites.
Previous studies of the star from the Karl G. Jansky Very Large Array in New Mexico revealed that the tiny star has a magnetic field several times stronger than the sun, although the physical processes that build the sun's magnetic field shouldn't work for such a small star.
"This star is a very different beast from our sun, magnetically speaking," CfA co-author Edo Berger said.
Williams and his team turned ALMA's powerful focus toward the tiny star, making the first detections of flarelike emissions from a red dwarf star at such high frequencies. The bursts of light created by the flares are 10,000 times brighter than those produced by the sun. Their presence in the short window of observations suggests that such flares are constantly being produced.
In their research, which has been accepted for publication in The Astrophysical Journal, the scientists named ALMA's extreme sensitivity as the key to detecting the flares. The measurement not only reveals more about the tiny star, but also opens the door to investigating other ultracool red dwarfs.
Bad news for life
If such emission is consistent across red dwarfs, it could mean bad news for the ability of life to evolve in the galaxy. Red dwarfs dominate the Milky Way, making up about three-fourths of all stars. Since NASA's Kepler telescope found planets around these worlds, the debate over whether or not they could host life has gone back and forth.
In order to hold liquid water on its surface, a condition necessary for life to evolve, a planet orbiting a dim red dwarf must lie significantly closer to its star than Earth lies to the sun. This region is known as the habitable zone. But its close proximity puts the planet at risk from stellar flares and coronal mass ejections, bursts of charged particles that stream out from a star. Stellar winds also carry charged particles away, potentially toward the planet.
If radiation reaches the surface of a planet, it can be damaging for any life growing there. Earth has a thick atmosphere that blocks most of the sun's rays, but the radiation that comes from orbiting very close to a red dwarf could tear away that type of protection. Plus, the extra-intense activity found around the ultracool red dwarf studied by Williams' team may make it even more challenging.
"It's like living in Tornado Alley in the U.S. Your location puts you at greater risk of severe storms," Williams said.
"A planet in the habitable zone of a star like this would be buffeted by storms much stronger than those generated by the sun."
Success! Japanese Spacecraft Arrives at Venus 5 Years After 1st Try (Dec 2015 Space.com)
A Japanese Venus probe took advantage of its long-awaited second chance.
Japan's Akatsuki spacecraft has arrived in orbit around Venus, five years after an engine failure scuttled its first attempt, Japanese Aerospace Exploration Agency (JAXA) officials announced today (Dec. 9).
The $300 million Akatsuki mission launched in May 2010 along with JAXA's IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) spacecraft, which became the first probe ever to deploy and use a solar sail in interplanetary space. .
Akatsuki was originally supposed to enter Venus orbit on Dec. 6, 2010, then study the planet's clouds, weather and atmosphere from above for at least two years to learn more about how the world became so hot and seemingly inhospitable to life. But the spacecraft's main engine conked out during a crucial orbit-insertion burn, and Akatsuki went zooming off into space.
The spacecraft — whose name means "Dawn" in Japanese — had been circling the sun for five years, waiting for another shot at Venus. That shot came exactly five years to the day after the first opportunity.
On Sunday (Dec. 6), Akatsuki fired its small attittude-control thrusters for 20 minutes to achieve Venus orbit (its main engine was pronounced dead long ago). After a few days of calculations and computations, mission controllers have now determined that the maneuver worked.
"The orbit period is 13 days and 14 hours. We also found that the orbiter is flying in the same direction as that of Venus's rotation," JAXA officials wrote in a statement today. "The Akatsuki is in good health."
Akatsuki's current path takes it as close as 250 miles (400 kilometers) to Venus, and as far away as 273,000 miles (440,000 km), officials added. This orbit is much more elliptical than the one Akatsuki was supposed to achieve five years ago, which featured a period of 30 hours and an apoapsis (most distant point from Venus) of 50,000 miles (80,000 km) or so.
Akatsuki's handlers will soon deploy and test three of the probe's six instruments, to make sure they're working properly — the other three are already known to be in good condition — and then conduct initial observations with all of this scientific gear for about three months, JAXA officials said.
At the same time, Akatsuki will maneuver to a less-elliptical final science orbit with a period of about nine days and an apoapsis around 193,000 miles (310,000 km). The probe should achieve that orbit, and commence regular operations, by April 2016.
Despite the long delay, the drama and the highly elliptical orbit, Akatsuki should still be able to accomplish most of its science goals, JAXA officials have said.
JAXA Mission website; http://global.jaxa.jp/projects/sat/planet_c/index.html
Tuesday 22 March 2016
NASA Telescopes Detect Jupiter-Like Storm on Small Star
"The star is the size of Jupiter, and its storm is the size of Jupiter's Great Red Spot," said John Gizis of the University of Delaware, Newark. "We know this newfound storm has lasted at least two years, and probably longer." Gizis is the lead author of a new study appearing in The Astrophysical Journal.
While planets have been known to have cloudy storms, this is the best evidence yet for a star that has one. The star, referred to as W1906+40, belongs to a thermally cool class of objects called L-dwarfs. Some L-dwarfs are considered stars because they fuse atoms and generate light, as our sun does, while others, called brown dwarfs, are known as "failed stars" for their lack of atomic fusion.
The L-dwarf in the study, W1906+40, is thought to be a star based on estimates of its age (the older the L-dwarf, the more likely it is a star). Its temperature is about 3,500 degrees Fahrenheit (2,200 Kelvin). That may sound scorching hot, but as far as stars go, it is relatively cool. Cool enough, in fact, for clouds to form in its atmosphere.
"The L-dwarf's clouds are made of tiny minerals," said Gizis.
Spitzer has observed other cloudy brown dwarfs before, finding evidence for short-lived storms lasting hours and perhaps days.
In the new study, the astronomers were able to study changes in the atmosphere of W1906+40 for two years. The L-dwarf had initially been discovered by NASA's Wide-field Infrared Survey Explorer in 2011. Later, Gizis and his team realized that this object happened to be located in the same area of the sky where NASA's Kepler mission had been staring at stars for years to hunt for planets.
Kepler identifies planets by looking for dips in starlight as planets pass in front of their stars. In this case, astronomers knew observed dips in starlight weren't coming from planets, but they thought they might be looking at a star spot -- which, like our sun's "sunspots," are a result of concentrated magnetic fields. Star spots would also cause dips in starlight as they rotate around the star.
Follow-up observations with Spitzer, which detects infrared light, revealed that the dark patch was not a magnetic star spot but a colossal, cloudy storm with a diameter that could hold three Earths. The storm rotates around the star about every 9 hours. Spitzer's infrared measurements at two infrared wavelengths probed different layers of the atmosphere and, together with the Kepler visible-light data, helped reveal the presence of the storm.
While this storm looks different when viewed at various wavelengths, astronomers say that if we could somehow travel there in a starship, it would look like a dark mark near the polar top of the star.
The researchers plan to look for other stormy stars and brown dwarfs using Spitzer and Kepler in the future.
"We don't know if this kind of star storm is unique or common, and we don't why it persists for so long," said Gizis.
NASA Mars Rover Curiosity Reaches Sand Dunes
A view of the rippled surface of what's been informally named "High Dune" is online at:
http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20168
A wheel track exposing material beneath the surface of a sand sheet nearby is at:
http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20169
The dunes close to Curiosity's current location are part of "Bagnold Dunes," a band along the northwestern flank of Mount Sharp inside Gale Crater. Observations of this dune field from orbit show that edges of individual dunes move as much as 3 feet (1 meter) per Earth year.
The rover's planned investigations include scooping a sample of the dune material for analysis with laboratory instruments inside Curiosity.
Curiosity has been working on Mars since early August 2012. It reached the base of Mount Sharp in 2014 after fruitfully investigating outcrops closer to its landing site and then trekking to the mountain. The main mission objective now is to examine successively higher layers of Mount Sharp.
For more information about Curiosity, visit:
http://mars.jpl.nasa.gov/msl
New Clues to Ceres' Bright Spots and Origins
About the Bright Spots
Ceres has more than 130 bright areas, and most of them are associated with impact craters. Study authors, led by Andreas Nathues at Max Planck Institute for Solar System Research, Göttingen, Germany, write that the bright material is consistent with a type of magnesium sulfate called hexahydrite. A different type of magnesium sulfate is familiar on Earth as Epsom salt.
Nathues and colleagues, using images from Dawn's framing camera, suggest that these salt-rich areas were left behind when water-ice sublimated in the past. Impacts from asteroids would have unearthed the mixture of ice and salt, they say.
"The global nature of Ceres' bright spots suggests that this world has a subsurface layer that contains briny water-ice," Nathues said.
A New Look at Occator
The surface of Ceres, whose average diameter is 584 miles (940 kilometers), is generally dark -- similar in brightness to fresh asphalt -- study authors wrote. The bright patches that pepper the surface represent a large range of brightness, with the brightest areas reflecting about 50 percent of sunlight shining on the area. But there has not been unambiguous detection of water ice on Ceres; higher-resolution data are needed to settle this question.
The inner portion of a crater called Occator contains the brightest material on Ceres. Occator itself is 60 miles (90 kilometers) in diameter, and its central pit, covered by this bright material, measures about 6 miles (10 kilometers) wide and 0.3 miles (0.5 kilometers) deep. Dark streaks, possibly fractures, traverse the pit. Remnants of a central peak, which was up to 0.3 miles (0.5 kilometers) high, can also be seen.
With its sharp rim and walls, and abundant terraces and landslide deposits, Occator appears to be among the youngest features on Ceres. Dawn mission scientists estimate its age to be about 78 million years old.
Study authors write that some views of Occator appear to show a diffuse haze near the surface that fills the floor of the crater. This may be associated with observations of water vapor at Ceres by the Herschel space observatory that were reported in 2014. The haze seems to be present in views during noon, local time, and absent at dawn and dusk, study authors write. This suggests that the phenomenon resembles the activity at the surface of a comet, with water vapor lifting tiny particles of dust and residual ice. Future data and analysis may test this hypothesis and reveal clues about the process causing this activity.
"The Dawn science team is still discussing these results and analyzing data to better understand what is happening at Occator," said Chris Russell, principal investigator of the Dawn mission, based at the University of California, Los Angeles.
The Importance of Ammonia
In the second Nature study, members of the Dawn science team examined the composition of Ceres and found evidence for ammonia-rich clays. They used data from the visible and infrared mapping spectrometer, a device that looks at how various wavelengths of light are reflected by the surface, allowing minerals to be identified.
Ammonia ice by itself would evaporate on Ceres today, because the dwarf planet is too warm. However, ammonia molecules could be stable if present in combination with (i.e. chemically bonded to) other minerals.
The presence of ammoniated compounds raises the possibility that Ceres did not originate in the main asteroid belt between Mars and Jupiter, where it currently resides, but instead might have formed in the outer solar system. Another idea is that Ceres formed close to its present position, incorporating materials that drifted in from the outer solar system - near the orbit of Neptune, where nitrogen ices are thermally stable.
"The presence of ammonia-bearing species suggests that Ceres is composed of material accreted in an environment where ammonia and nitrogen were abundant. Consequently, we think that this material originated in the outer cold solar system," said Maria Cristina De Sanctis, lead author of the study, based at the National Institute of Astrophysics, Rome.
In comparing the spectrum of reflected light from Ceres to meteorites, scientists found some similarities. Specifically, they focused on the spectra, or chemical fingerprints, of carbonaceous chondrites, a type of carbon-rich meteorite thought to be relevant analogues for the dwarf planet. But these are not good matches for all wavelengths that the instrument sampled, the team found. In particular, there were distinctive absorption bands, matching mixtures containing ammoniated minerals, associated with wavelengths that can't be observed from Earth-based telescopes.
The scientists note another difference is that these carbonaceous chondrites have bulk water contents of 15 to 20 percent, while Ceres' content is as much as 30 percent.
"Ceres may have retained more volatiles than these meteorites, or it could have accreted the water from volatile-rich material," De Sanctis said.
The study also shows that daytime surface temperatures on Ceres span from minus 136 degrees to minus 28 degrees Fahrenheit (180 to 240 Kelvin). The maximum temperatures were measured in the equatorial region. The temperatures at and near the equator are generally too high to support ice at the surface for a long time, study authors say, but data from Dawn's next orbit will reveal more details.
As of this week, Dawn has reached its final orbital altitude at Ceres, about 240 miles (385 kilometers) from the surface of the dwarf planet. In mid-December, Dawn will begin taking observations from this orbit, including images at a resolution of 120 feet (35 meters) per pixel, infrared, gamma ray and neutron spectra, and high-resolution gravity data.
NASA Juno Cam Platform Opened Up
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:
"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:
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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