Thursday 22 December 2016
Visions of Our Solar System (Natural History Museum, early 2016. Sunday Times Magazine)
Just a couple of pictures which struck me as quite beautiful, for the exhibition earlier in the year.
George Mueller Obituary (The Guardian)
One of the lesser known characters in the Apollo story - but still found his obituary interesting.
Comet 67P (The Guardian)
Catching up on some old stuff which I had saved to post on the blog.
Loved this picture, from an aesthetic and scientific point of view. In addition, text described well the picture to a non-science audience.
Loved this picture, from an aesthetic and scientific point of view. In addition, text described well the picture to a non-science audience.
Monday 19 December 2016
Ten Years of Discovery by Mars Reconnaissance Orbiter - Movie (NASA)
Fantastic, detailed imagery celebrating Mars Reconnaissance's 10 years of operation.
Mars Reconnaissance Orbiter movie link
Mars Reconnaissance Orbiter movie link
 |
| Ahuna Mons seen from LAMO |
One year ago, on March 6, 2015, NASA's Dawn spacecraft slid gently into orbit around Ceres, the largest body in the asteroid belt between Mars and Jupiter. Since then, the spacecraft has delivered a wealth of images and other data that open an exciting new window to the previously unexplored dwarf planet.
"Ceres has defied our expectations and surprised us in many ways, thanks to a year's worth of data from Dawn. We are hard at work on the mysteries the spacecraft has presented to us," said Carol Raymond, deputy principal investigator for the mission, based at NASA's Jet Propulsion Laboratory, Pasadena, California.
Among Ceres' most enigmatic features is a tall mountain the Dawn team named Ahuna Mons. This mountain appeared as a small, bright-sided bump on the surface as early as February 2015 from a distance of 29,000 miles (46,000 kilometers), before Dawn was captured into orbit. As Dawn circled Ceres at increasingly lower altitudes, the shape of this mysterious feature began to come into focus. From afar, Ahuna Mons looked to be pyramid-shaped, but upon closer inspection, it is best described as a dome with smooth, steep walls.
Dawn's latest images of Ahuna Mons, taken 120 times closer than in February 2015, reveal that this mountain has a lot of bright material on some of its slopes, and less on others. On its steepest side, it is about 3 miles (5 kilometers) high. The mountain has an average overall height of 2.5 miles (4 kilometers). It rises higher than Washington's Mount Rainier and California's Mount Whitney.
Scientists are beginning to identify other features on Ceres that could be similar in nature to Ahuna Mons, but none is as tall and well-defined as this mountain.
"No one expected a mountain on Ceres, especially one like Ahuna Mons," said Chris Russell, Dawn's principal investigator at the University of California, Los Angeles. "We still do not have a satisfactory model to explain how it formed."
About 420 miles (670 kilometers) northwest of Ahuna Mons lies the now-famous Occator Crater. Before Dawn arrived at Ceres, images of the dwarf planet from NASA's Hubble Space Telescope showed a prominent bright patch on the surface. As Dawn approached Ceres, it became clear that there were at least two spots with high reflectivity. As the resolution of images improved, Dawn revealed to its earthly followers that there are at least 10 bright spots in this crater alone, with the brightest area on the entire body located in the center of the crater. It is not yet clear whether this bright material is the same as the material found on Ahuna Mons.
"Dawn began mapping Ceres at its lowest altitude in December, but it wasn't until very recently that its orbital path allowed it to view Occator's brightest area. This dwarf planet is very large and it takes a great many orbital revolutions before all of it comes into view of Dawn's camera and other sensors," said Marc Rayman, Dawn's chief engineer and mission director at JPL.
Researchers will present new images and other insights about Ceres at the 47th Lunar and Planetary Science Conference, during a press briefing on March 22 in The Woodlands, Texas.
When it arrived at Ceres on March 6, 2015, Dawn made history as the first mission to reach a dwarf planet, and the first to orbit two distinct extraterrestrial targets. The mission conducted extensive observations of Vesta in 2011-2012.
Dawn's mission is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team. For a complete list of mission participants, visit:
http://dawn.jpl.nasa.gov/mission
More information about Dawn is available at the following sites:
http://dawn.jpl.nasa.gov
Conditions for life may hinge on how fast the universe is expanding (AAAS)
Scientists have known for several years now that stars, galaxies, and almost everything in the universe is moving away from us (and from everything else) at a faster and faster pace. Now, it turns out that the unknown forces behind the rate of this accelerating expansion—a mathematical value called the cosmological constant—may play a previously unexplored role in creating the right conditions for life.
That’s the conclusion of a group of physicists who studied the effects of massive cosmic explosions, called gamma ray bursts, on planets. They found that when it comes to growing life, it’s better to be far away from your neighbors—and the cosmological constant helps thin out the neighborhood.
“In dense environments, you have many explosions, and you’re too close to them,” says cosmologist and theoretical physicist Raul Jimenez of the University of Barcelona in Spain and an author on the new study. “It’s best to be in the outskirts, or in regions that have not been highly populated by small galaxies—and that’s exactly where the Milky Way is.”
Jimenez and his team had previously shown that gamma ray bursts could cause mass extinctions or make planets inhospitable to life by zapping them with radiation and destroying their ozone layer. The bursts channel the radiation into tight beams so powerful that one of them sweeping through a star system could wipe out planets in another galaxy. For their latest work, published this month in Physical Review Letters, they wanted to apply those findings on a broader scale and determine what type of universe would be most likely to support life.
The research is the latest investigation to touch on the so-called anthropic principle: the idea that in some sense the universe is tuned for the emergence of intelligent life. If the forces of nature were much stronger or weaker than physicists observe, proponents note, crucial building blocks of life—such fundamental particles, atoms, or the long-chain molecules needed for the chemistry of life—might not have formed, resulting in a sterile or even completely chaotic universe. Some researchers have tried to gauge how much “wiggle room” various physical constants might have for change before making the cosmos unrecognizable and uninhabitable. Others, however, question what such research really means and whether it is worthwhile.
Jimenez and colleagues tackled one, large-scale facet of the anthropic principle. They used a computer model to run simulations of the universe expanding and accelerating at many different speeds. They then measured how changing the cosmological constant affected the universe’s density, paying particular attention to what that meant about gamma ray bursts raining down radiation on stars and planets.
As it turns out, our universe seems to get it just about right. The existing cosmological constant means the rate of expansion is large enough that it minimizes planets’ exposure to gamma ray bursts, but small enough to form lots of hydrogen-burning stars around which life can exist. (A faster expansion rate would make it hard for gas clouds to collapse into stars.)
Jimenez says the expansion of the universe played a bigger role in creating habitable worlds than he expected. “It was surprising to me that you do need the cosmological constant to clear out the region and make it more suburbanlike,” he says.
Beyond what they reveal about the potential for life in our galaxy and beyond, the findings offer a new nugget of insight into one of the biggest puzzles in cosmology: why the cosmological constant is what it is, says cosmologist Alan Heavens, director of the Imperial Centre for Inference and Cosmology at Imperial College London.
In theory, Heavens explains, either the constant should be hundreds of orders of magnitude higher than it appears to be, or it should be zero, in which case the universe wouldn’t accelerate. But this would disagree with what astronomers have observed. “The small—but nonzero—size of the cosmological constant is a real puzzle in cosmology,” he says, adding that the research shows the number is consistent with the conditions required for the existence of intelligent life that is capable of observing it.
Lee Smolin, a theoretical physicist at Perimeter Institute for Theoretical Physics in Waterloo, Canada, and a skeptic of the anthropic principle, says the paper’s argument is a novel one and that on first reading he didn’t see any obvious mistakes. “I’ve not heard it before, so they’re to be praised for making a new argument,” he says.
However, he adds, all truly anthropic arguments to date fall back on fallacies or circular reasoning. For example, many tend to cherry-pick by looking only at one variable in the development of life at a time; looking at several variables at once could lead to a different conclusion.
Jimenez says the next step is to investigate whether gamma ray bursts are really as devastating to life as scientists believe. His team’s work has shown only that exposure to such massive bursts of radiation would almost certainly peel away a planet’s protective ozone layer. “Is this going to be catastrophic to life?” he says. “I think so, but it may be that life is more resilient than we think.”
That’s the conclusion of a group of physicists who studied the effects of massive cosmic explosions, called gamma ray bursts, on planets. They found that when it comes to growing life, it’s better to be far away from your neighbors—and the cosmological constant helps thin out the neighborhood.
“In dense environments, you have many explosions, and you’re too close to them,” says cosmologist and theoretical physicist Raul Jimenez of the University of Barcelona in Spain and an author on the new study. “It’s best to be in the outskirts, or in regions that have not been highly populated by small galaxies—and that’s exactly where the Milky Way is.”
Jimenez and his team had previously shown that gamma ray bursts could cause mass extinctions or make planets inhospitable to life by zapping them with radiation and destroying their ozone layer. The bursts channel the radiation into tight beams so powerful that one of them sweeping through a star system could wipe out planets in another galaxy. For their latest work, published this month in Physical Review Letters, they wanted to apply those findings on a broader scale and determine what type of universe would be most likely to support life.
The research is the latest investigation to touch on the so-called anthropic principle: the idea that in some sense the universe is tuned for the emergence of intelligent life. If the forces of nature were much stronger or weaker than physicists observe, proponents note, crucial building blocks of life—such fundamental particles, atoms, or the long-chain molecules needed for the chemistry of life—might not have formed, resulting in a sterile or even completely chaotic universe. Some researchers have tried to gauge how much “wiggle room” various physical constants might have for change before making the cosmos unrecognizable and uninhabitable. Others, however, question what such research really means and whether it is worthwhile.
Jimenez and colleagues tackled one, large-scale facet of the anthropic principle. They used a computer model to run simulations of the universe expanding and accelerating at many different speeds. They then measured how changing the cosmological constant affected the universe’s density, paying particular attention to what that meant about gamma ray bursts raining down radiation on stars and planets.
As it turns out, our universe seems to get it just about right. The existing cosmological constant means the rate of expansion is large enough that it minimizes planets’ exposure to gamma ray bursts, but small enough to form lots of hydrogen-burning stars around which life can exist. (A faster expansion rate would make it hard for gas clouds to collapse into stars.)
Jimenez says the expansion of the universe played a bigger role in creating habitable worlds than he expected. “It was surprising to me that you do need the cosmological constant to clear out the region and make it more suburbanlike,” he says.
Beyond what they reveal about the potential for life in our galaxy and beyond, the findings offer a new nugget of insight into one of the biggest puzzles in cosmology: why the cosmological constant is what it is, says cosmologist Alan Heavens, director of the Imperial Centre for Inference and Cosmology at Imperial College London.
In theory, Heavens explains, either the constant should be hundreds of orders of magnitude higher than it appears to be, or it should be zero, in which case the universe wouldn’t accelerate. But this would disagree with what astronomers have observed. “The small—but nonzero—size of the cosmological constant is a real puzzle in cosmology,” he says, adding that the research shows the number is consistent with the conditions required for the existence of intelligent life that is capable of observing it.
Lee Smolin, a theoretical physicist at Perimeter Institute for Theoretical Physics in Waterloo, Canada, and a skeptic of the anthropic principle, says the paper’s argument is a novel one and that on first reading he didn’t see any obvious mistakes. “I’ve not heard it before, so they’re to be praised for making a new argument,” he says.
However, he adds, all truly anthropic arguments to date fall back on fallacies or circular reasoning. For example, many tend to cherry-pick by looking only at one variable in the development of life at a time; looking at several variables at once could lead to a different conclusion.
Jimenez says the next step is to investigate whether gamma ray bursts are really as devastating to life as scientists believe. His team’s work has shown only that exposure to such massive bursts of radiation would almost certainly peel away a planet’s protective ozone layer. “Is this going to be catastrophic to life?” he says. “I think so, but it may be that life is more resilient than we think.”
Gravitational Waves Detected 100 Years After Einstein's Prediction (LIGO)
For the first time, scientists have observed ripples in the fabric of spacetime called gravitational waves, arriving at the earth from a cataclysmic event in the distant universe. This confirms a major prediction of Albert Einstein’s 1915 general theory of relativity and opens an unprecedented new window onto the cosmos.
Gravitational waves carry information about their dramatic origins and about the nature of gravity that cannot otherwise be obtained. Physicists have concluded that the detected gravitational waves were produced during the final fraction of a second of the merger of two black holes to produce a single, more massive spinning black hole. This collision of two black holes had been predicted but never observed.
The gravitational waves were detected on September 14, 2015 at 5:51 a.m. Eastern Daylight Time (09:51 UTC) by both of the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington, USA. The LIGO Observatories are funded by the National Science Foundation (NSF), and were conceived, built, and are operated by Caltech and MIT. The discovery, accepted for publication in the journal Physical Review Letters, was made by the LIGO Scientific Collaboration (which includes the GEO Collaboration and the Australian Consortium for Interferometric Gravitational Astronomy) and the Virgo Collaboration using data from the two LIGO detectors.
Based on the observed signals, LIGO scientists estimate that the black holes for this event were about 29 and 36 times the mass of the sun, and the event took place 1.3 billion years ago. About 3 times the mass of the sun was converted into gravitational waves in a fraction of a second—with a peak power output about 50 times that of the whole visible universe. By looking at the time of arrival of the signals—the detector in Livingston recorded the event 7 milliseconds before the detector in Hanford—scientists can say that the source was located in the Southern Hemisphere.
According to general relativity, a pair of black holes orbiting around each other lose energy through the emission of gravitational waves, causing them to gradually approach each other over billions of years, and then much more quickly in the final minutes. During the final fraction of a second, the two black holes collide into each other at nearly one-half the speed of light and form a single more massive black hole, converting a portion of the combined black holes’ mass to energy, according to Einstein’s formula E=mc2. This energy is emitted as a final strong burst of gravitational waves. It is these gravitational waves that LIGO has observed.
The existence of gravitational waves was first demonstrated in the 1970s and 80s by Joseph Taylor, Jr., and colleagues. Taylor and Russell Hulse discovered in 1974 a binary system composed of a pulsar in orbit around a neutron star. Taylor and Joel M. Weisberg in 1982 found that the orbit of the pulsar was slowly shrinking over time because of the release of energy in the form of gravitational waves. For discovering the pulsar and showing that it would make possible this particular gravitational wave measurement, Hulse and Taylor were awarded the Nobel Prize in Physics in 1993.
The new LIGO discovery is the first observation of gravitational waves themselves, made by measuring the tiny disturbances the waves make to space and time as they pass through the earth.
“Our observation of gravitational waves accomplishes an ambitious goal set out over 5 decades ago to directly detect this elusive phenomenon and better understand the universe, and, fittingly, fulfills Einstein’s legacy on the 100th anniversary of his general theory of relativity,” says Caltech’s David H. Reitze, executive director of the LIGO Laboratory.
The discovery was made possible by the enhanced capabilities of Advanced LIGO, a major upgrade that increases the sensitivity of the instruments compared to the first generation LIGO detectors, enabling a large increase in the volume of the universe probed—and the discovery of gravitational waves during its first observation run. The US National Science Foundation leads in financial support for Advanced LIGO. Funding organizations in Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council, STFC) and Australia (Australian Research Council) also have made significant commitments to the project. Several of the key technologies that made Advanced LIGO so much more sensitive have been developed and tested by the German UK GEO collaboration. Significant computer resources have been contributed by the AEI Hannover Atlas Cluster, the LIGO Laboratory, Syracuse University, and the University of Wisconsin- Milwaukee. Several universities designed, built, and tested key components for Advanced LIGO: The Australian National University, the University of Adelaide, the University of Florida, Stanford University, Columbia University of the City of New York, and Louisiana State University.
“In 1992, when LIGO’s initial funding was approved, it represented the biggest investment the NSF had ever made,” says France Córdova, NSF director. “It was a big risk. But the National Science Foundation is the agency that takes these kinds of risks. We support fundamental science and engineering at a point in the road to discovery where that path is anything but clear. We fund trailblazers. It’s why the U.S. continues to be a global leader in advancing knowledge.”
LIGO research is carried out by the LIGO Scientific Collaboration (LSC), a group of more than 1000 scientists from universities around the United States and in 14 other countries. More than 90 universities and research institutes in the LSC develop detector technology and analyze data; approximately 250 students are strong contributing members of the collaboration. The LSC detector network includes the LIGO interferometers and the GEO600 detector. The GEO team includes scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI), Leibniz Universität Hannover, along with partners at the University of Glasgow, Cardiff University, the University of Birmingham, other universities in the United Kingdom, and the University of the Balearic Islands in Spain.
“This detection is the beginning of a new era: The field of gravitational wave astronomy is now a reality,” says Gabriela González, LSC spokesperson and professor of physics and astronomy at Louisiana State University.
LIGO was originally proposed as a means of detecting these gravitational waves in the 1980s by Rainer Weiss, professor of physics, emeritus, from MIT; Kip Thorne, Caltech’s Richard P. Feynman Professor of Theoretical Physics, emeritus; and Ronald Drever, professor of physics, emeritus, also from Caltech.
“The description of this observation is beautifully described in the Einstein theory of general relativity formulated 100 years ago and comprises the first test of the theory in strong gravitation. It would have been wonderful to watch Einstein’s face had we been able to tell him,” says Weiss.
“With this discovery, we humans are embarking on a marvelous new quest: the quest to explore the warped side of the universe—objects and phenomena that are made from warped spacetime. Colliding black holes and gravitational waves are our first beautiful examples,” says Thorne.
Virgo research is carried out by the Virgo Collaboration, consisting of more than 250 physicists and engineers belonging to 19 different European research groups: 6 from Centre National de la Recherche Scientifique (CNRS) in France; 8 from the Istituto Nazionale di Fisica Nucleare (INFN) in Italy; 2 in The Netherlands with Nikhef; the Wigner RCP in Hungary; the POLGRAW group in Poland; and the European Gravitational Observatory (EGO), the laboratory hosting the Virgo detector near Pisa in Italy.
Fulvio Ricci, Virgo Spokesperson, notes that, “This is a significant milestone for physics, but more importantly merely the start of many new and exciting astrophysical discoveries to come with LIGO and Virgo.”
Bruce Allen, managing director of the Max Planck Institute for Gravitational Physics (Albert Einstein Institute), adds, “Einstein thought gravitational waves were too weak to detect, and didn’t believe in black holes. But I don’t think he’d have minded being wrong!”
“The Advanced LIGO detectors are a tour de force of science and technology, made possible by a truly exceptional international team of technicians, engineers, and scientists,” says David Shoemaker of MIT, the project leader for Advanced LIGO. “We are very proud that we finished this NSF-funded project on time and on budget.”
At each observatory, the two-and-a-half-mile (4-km) long L-shaped LIGO interferometer uses laser light split into two beams that travel back and forth down the arms (four-foot diameter tubes kept under a near-perfect vacuum). The beams are used to monitor the distance between mirrors precisely positioned at the ends of the arms. According to Einstein’s theory, the distance between the mirrors will change by an infinitesimal amount when a gravitational wave passes by the detector. A change in the lengths of the arms smaller than one-ten-thousandth the diameter of a proton (10-19 meter) can be detected.
“To make this fantastic milestone possible took a global collaboration of scientists—laser and suspension technology developed for our GEO600 detector was used to help make Advanced LIGO the most sophisticated gravitational wave detector ever created,” says Sheila Rowan, professor of physics and astronomy at the University of Glasgow.
Independent and widely separated observatories are necessary to determine the direction of the event causing the gravitational waves, and also to verify that the signals come from space and are not from some other local phenomenon.
Toward this end, the LIGO Laboratory is working closely with scientists in India at the Inter-University Centre for Astronomy and Astrophysics, the Raja Ramanna Centre for Advanced Technology, and the Institute for Plasma to establish a third Advanced LIGO detector on the Indian subcontinent. Awaiting approval by the government of India, it could be operational early in the next decade. The additional detector will greatly improve the ability of the global detector network to localize gravitational-wave sources.
“Hopefully this first observation will accelerate the construction of a global network of detectors to enable accurate source location in the era of multi-messenger astronomy,” says David McClelland, professor of physics and director of the Centre for Gravitational Physics at the Australian National University.
Additional video and image assets can be found here: http://mediaassets.caltech.edu/gwave
Gravitational waves carry information about their dramatic origins and about the nature of gravity that cannot otherwise be obtained. Physicists have concluded that the detected gravitational waves were produced during the final fraction of a second of the merger of two black holes to produce a single, more massive spinning black hole. This collision of two black holes had been predicted but never observed.
The gravitational waves were detected on September 14, 2015 at 5:51 a.m. Eastern Daylight Time (09:51 UTC) by both of the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington, USA. The LIGO Observatories are funded by the National Science Foundation (NSF), and were conceived, built, and are operated by Caltech and MIT. The discovery, accepted for publication in the journal Physical Review Letters, was made by the LIGO Scientific Collaboration (which includes the GEO Collaboration and the Australian Consortium for Interferometric Gravitational Astronomy) and the Virgo Collaboration using data from the two LIGO detectors.
Based on the observed signals, LIGO scientists estimate that the black holes for this event were about 29 and 36 times the mass of the sun, and the event took place 1.3 billion years ago. About 3 times the mass of the sun was converted into gravitational waves in a fraction of a second—with a peak power output about 50 times that of the whole visible universe. By looking at the time of arrival of the signals—the detector in Livingston recorded the event 7 milliseconds before the detector in Hanford—scientists can say that the source was located in the Southern Hemisphere.
According to general relativity, a pair of black holes orbiting around each other lose energy through the emission of gravitational waves, causing them to gradually approach each other over billions of years, and then much more quickly in the final minutes. During the final fraction of a second, the two black holes collide into each other at nearly one-half the speed of light and form a single more massive black hole, converting a portion of the combined black holes’ mass to energy, according to Einstein’s formula E=mc2. This energy is emitted as a final strong burst of gravitational waves. It is these gravitational waves that LIGO has observed.
The existence of gravitational waves was first demonstrated in the 1970s and 80s by Joseph Taylor, Jr., and colleagues. Taylor and Russell Hulse discovered in 1974 a binary system composed of a pulsar in orbit around a neutron star. Taylor and Joel M. Weisberg in 1982 found that the orbit of the pulsar was slowly shrinking over time because of the release of energy in the form of gravitational waves. For discovering the pulsar and showing that it would make possible this particular gravitational wave measurement, Hulse and Taylor were awarded the Nobel Prize in Physics in 1993.
The new LIGO discovery is the first observation of gravitational waves themselves, made by measuring the tiny disturbances the waves make to space and time as they pass through the earth.
“Our observation of gravitational waves accomplishes an ambitious goal set out over 5 decades ago to directly detect this elusive phenomenon and better understand the universe, and, fittingly, fulfills Einstein’s legacy on the 100th anniversary of his general theory of relativity,” says Caltech’s David H. Reitze, executive director of the LIGO Laboratory.
The discovery was made possible by the enhanced capabilities of Advanced LIGO, a major upgrade that increases the sensitivity of the instruments compared to the first generation LIGO detectors, enabling a large increase in the volume of the universe probed—and the discovery of gravitational waves during its first observation run. The US National Science Foundation leads in financial support for Advanced LIGO. Funding organizations in Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council, STFC) and Australia (Australian Research Council) also have made significant commitments to the project. Several of the key technologies that made Advanced LIGO so much more sensitive have been developed and tested by the German UK GEO collaboration. Significant computer resources have been contributed by the AEI Hannover Atlas Cluster, the LIGO Laboratory, Syracuse University, and the University of Wisconsin- Milwaukee. Several universities designed, built, and tested key components for Advanced LIGO: The Australian National University, the University of Adelaide, the University of Florida, Stanford University, Columbia University of the City of New York, and Louisiana State University.
“In 1992, when LIGO’s initial funding was approved, it represented the biggest investment the NSF had ever made,” says France Córdova, NSF director. “It was a big risk. But the National Science Foundation is the agency that takes these kinds of risks. We support fundamental science and engineering at a point in the road to discovery where that path is anything but clear. We fund trailblazers. It’s why the U.S. continues to be a global leader in advancing knowledge.”
LIGO research is carried out by the LIGO Scientific Collaboration (LSC), a group of more than 1000 scientists from universities around the United States and in 14 other countries. More than 90 universities and research institutes in the LSC develop detector technology and analyze data; approximately 250 students are strong contributing members of the collaboration. The LSC detector network includes the LIGO interferometers and the GEO600 detector. The GEO team includes scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI), Leibniz Universität Hannover, along with partners at the University of Glasgow, Cardiff University, the University of Birmingham, other universities in the United Kingdom, and the University of the Balearic Islands in Spain.
“This detection is the beginning of a new era: The field of gravitational wave astronomy is now a reality,” says Gabriela González, LSC spokesperson and professor of physics and astronomy at Louisiana State University.
LIGO was originally proposed as a means of detecting these gravitational waves in the 1980s by Rainer Weiss, professor of physics, emeritus, from MIT; Kip Thorne, Caltech’s Richard P. Feynman Professor of Theoretical Physics, emeritus; and Ronald Drever, professor of physics, emeritus, also from Caltech.
“The description of this observation is beautifully described in the Einstein theory of general relativity formulated 100 years ago and comprises the first test of the theory in strong gravitation. It would have been wonderful to watch Einstein’s face had we been able to tell him,” says Weiss.
“With this discovery, we humans are embarking on a marvelous new quest: the quest to explore the warped side of the universe—objects and phenomena that are made from warped spacetime. Colliding black holes and gravitational waves are our first beautiful examples,” says Thorne.
Virgo research is carried out by the Virgo Collaboration, consisting of more than 250 physicists and engineers belonging to 19 different European research groups: 6 from Centre National de la Recherche Scientifique (CNRS) in France; 8 from the Istituto Nazionale di Fisica Nucleare (INFN) in Italy; 2 in The Netherlands with Nikhef; the Wigner RCP in Hungary; the POLGRAW group in Poland; and the European Gravitational Observatory (EGO), the laboratory hosting the Virgo detector near Pisa in Italy.
Fulvio Ricci, Virgo Spokesperson, notes that, “This is a significant milestone for physics, but more importantly merely the start of many new and exciting astrophysical discoveries to come with LIGO and Virgo.”
Bruce Allen, managing director of the Max Planck Institute for Gravitational Physics (Albert Einstein Institute), adds, “Einstein thought gravitational waves were too weak to detect, and didn’t believe in black holes. But I don’t think he’d have minded being wrong!”
“The Advanced LIGO detectors are a tour de force of science and technology, made possible by a truly exceptional international team of technicians, engineers, and scientists,” says David Shoemaker of MIT, the project leader for Advanced LIGO. “We are very proud that we finished this NSF-funded project on time and on budget.”
At each observatory, the two-and-a-half-mile (4-km) long L-shaped LIGO interferometer uses laser light split into two beams that travel back and forth down the arms (four-foot diameter tubes kept under a near-perfect vacuum). The beams are used to monitor the distance between mirrors precisely positioned at the ends of the arms. According to Einstein’s theory, the distance between the mirrors will change by an infinitesimal amount when a gravitational wave passes by the detector. A change in the lengths of the arms smaller than one-ten-thousandth the diameter of a proton (10-19 meter) can be detected.
“To make this fantastic milestone possible took a global collaboration of scientists—laser and suspension technology developed for our GEO600 detector was used to help make Advanced LIGO the most sophisticated gravitational wave detector ever created,” says Sheila Rowan, professor of physics and astronomy at the University of Glasgow.
Independent and widely separated observatories are necessary to determine the direction of the event causing the gravitational waves, and also to verify that the signals come from space and are not from some other local phenomenon.
Toward this end, the LIGO Laboratory is working closely with scientists in India at the Inter-University Centre for Astronomy and Astrophysics, the Raja Ramanna Centre for Advanced Technology, and the Institute for Plasma to establish a third Advanced LIGO detector on the Indian subcontinent. Awaiting approval by the government of India, it could be operational early in the next decade. The additional detector will greatly improve the ability of the global detector network to localize gravitational-wave sources.
“Hopefully this first observation will accelerate the construction of a global network of detectors to enable accurate source location in the era of multi-messenger astronomy,” says David McClelland, professor of physics and director of the Centre for Gravitational Physics at the Australian National University.
Additional video and image assets can be found here: http://mediaassets.caltech.edu/gwave
Particles in Love: Quantum Mechanics Explored in New Study (NASA)
Here's a love story at the smallest scales imaginable: particles of light. It is possible to have particles that are so intimately linked that a change to one affects the other, even when they are separated at a distance.
This idea, called "entanglement," is part of the branch of physics called quantum mechanics, a description of the way the world works at the level of atoms and particles that are even smaller. Quantum mechanics says that at these very tiny scales, some properties of particles are based entirely on probability. In other words, nothing is certain until it happens.
Testing Bell's Theorem
Albert Einstein did not entirely believe that the laws of quantum mechanics described reality. He and others postulated that there must be some hidden variables at work, which would allow quantum systems to be predictable. In 1964, however, John Bell published the idea that any model of physical reality with such hidden variables also must allow for the instantaneous influence of one particle on another. While Einstein proved that information cannot travel faster than the speed of light, particles can still affect each other when they are far apart according to Bell.
Scientists consider Bell's theorem an important foundation for modern physics. While many experiments have taken place to try to prove his theorem, no one was able to run a full, proper test of the experiment Bell would have needed until recently. In 2015, three separate studies were published on this topic, all consistent with the predictions of quantum mechanics and entanglement.
"What's exciting is that in some sense, we're doing experimental philosophy," said Krister Shalm, physicist with the National Institute of Standards and Technology (NIST), Boulder, Colorado. Shalm is lead author on one of the 2015 studies testing Bell's theorem. "Humans have always had certain expectations of how the world works, and when quantum mechanics came along, it seemed to behave differently."
How 'Alice and Bob' Test Quantum Mechanics
The paper by Shalm, Marsili and colleagues was published in the journal Physical Review Letters, with the mind-bending title "Strong Loophole-Free Test of Local Realism."
"Our paper and the other two published last year show that Bell was right: any model of the world that contains hidden variables must also allow for entangled particles to influence one another at a distance," said Francesco Marsili of NASA's Jet Propulsion Laboratory in Pasadena, California, who collaborated with Shalm.
An analogy helps to understand the experiment, which was conducted at a NIST laboratory in Boulder:
Imagine that A and B are entangled photons. A is sent to Alice and B is sent to Bob, who are located 607 feet (185 meters) apart.
Alice and Bob poke and prod at their photons in all kinds of ways to get a sense of their properties. Without talking to each other, they then each randomly decide how to measure their photons, using random number generators to guide their decisions. When Alice and Bob compare notes, they are surprised to find that the results of their independent experiments are correlated. In other words, even at a distance, measuring one photon of the entangled pair affects the properties of the other photon.
"It's as if Alice and Bob try to tear the two photons apart, but their love still persists," Shalm said. In other words, the entangled photons behave as if they are two parts of a single system, even when separated in space.
Alice and Bob -- representing actual photon detectors -- then repeat this with many other pairs of entangled photons, and the phenomenon persists.
In reality, the photon detectors are not people, but superconducting nanowire single photon detectors (SNSPDs). SNSPDs are metal strips that are cooled until they become "superconducting," meaning they lose their electric resistance. A photon hitting this strip causes it to turn into a normal metal again momentarily, so the resistance of the strip jumps from zero to a finite value. This change in resistance allows the researchers to record the event.
To make this experiment happen in a laboratory, the big challenge is to avoid losing photons as they get sent to the Alice and Bob detectors through an optical fiber. JPL and NIST developed SNSPDs with worldrecord performance, demonstrating more than 90 percent efficiency and low "jitter," or uncertainty on the time of arrival of a photon. This experiment would not have been possible without SNSPDs.
Why This is Useful
The design of this experiment could potentially be used in cryptography -- making information and communications secure -- as it involves generating random numbers.
"The same experiment that tells us something deep about how the world is constructed also can be used for these applications that require you to keep your information safe," Shalm said.
Cryptography isn't the only application of this research. Detectors similar to those used for the experiment, which were built by JPL and NIST, could eventually also be used for deep-space optical communication. With a high efficiency and low uncertainty about the time of signal arrival, these detectors are well-suited for transmitting information with pulses of light in the optical spectrum.
"Right now we have the Deep Space Network to communicate with spacecraft around the solar system, which encodes information in radio signals. With optical communications, we could increase the data rate of that network 10- to 100-fold," Marsili said.
Deep space optical communication using technology similar to the detectors in Marsili's experiment was demonstrated with NASA's Lunar Atmosphere Dust and Environment Explorer (LADEE) mission, which orbited the moon from October 2013 to April 2014. A technology mission called the Lunar Laser Communication Demonstration, with components on LADEE and on the ground, downlinked data encoded in laser pulses, and made use of ground receivers based on SNSPDs.
NASA's Space Technology Mission Directorate is working on the Laser Communications Relay Demonstration (LCRD) mission. The mission proposes to revolutionize the way we send and receive data, video and other information, using lasers to encode and transmit data at rates 10 to 100 times faster than today's fastest radio-frequency systems, using significantly less mass and power.
"Information can never travel faster than the speed of light -- Einstein was right about that. But through optical communications research, we can increase the amount of information we send back from space," Marsili said. "The fact that the detectors from our experiment have this application creates great synergy between the two endeavors."
And so, what began as the study of "love" between particles is contributing to innovations in communications between space and Earth. "Love makes the world go 'round," and it may, in a sense, help us learn about other worlds.
Saturn's Rings: Less than Meets the Eye? (NASA)
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| Tethys in top left of image.
It seems intuitive that an opaque material should contain more stuff than a more translucent substance. For example, muddier water has more suspended particles of dirt in it than clearer water. Likewise, you might think that, in the rings of Saturn, more opaque areas contain a greater concentration of material than places where the rings seem more transparent.
But this intuition does not always apply, according to a recent study of the rings using data from NASA's Cassini mission. In their analysis, scientists found surprisingly little correlation between how dense a ring might appear to be -- in terms of its opacity and reflectiveness -- and the amount of material it contains.
The new results concern Saturn's B ring, the brightest and most opaque of Saturn's rings, and are consistent with previous studies that found similar results for Saturn's other main rings.
The scientists found that, while the opacity of the B ring varied by a large amount across its width, the mass - or amount of material - did not vary much from place to place. They "weighed" the nearly opaque center of the B ring for the first time -- technically, they determined its mass density in several places -- by analyzing spiral density waves. These are fine-scale ring features created by gravity tugging on ring particles from Saturn's moons, and the planet's own gravity. The structure of each wave depends directly on the amount of mass in the part of the rings where the wave is located.
"At present it's far from clear how regions with the same amount of material can have such different opacities. It could be something associated with the size or density of individual particles, or it could have something to do with the structure of the rings," said Matthew Hedman, the study's lead author and a Cassini participating scientist at the University of Idaho, Moscow. Cassini co-investigator Phil Nicholson of Cornell University, Ithaca, New York, co-authored the work with Hedman.
"Appearances can be deceiving," said Nicholson. "A good analogy is how a foggy meadow is much more opaque than a swimming pool, even though the pool is denser and contains a lot more water."
Research on the mass of Saturn's rings has important implications for their age. A less massive ring would evolve faster than a ring containing more material, becoming darkened by dust from meteorites and other cosmic sources more quickly. Thus, the less massive the B ring is, the younger it might be -- perhaps a few hundred million years instead of a few billion.
"By 'weighing' the core of the B ring for the first time, this study makes a meaningful step in our quest to piece together the age and origin of Saturn's rings," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory, Pasadena, California. "The rings are so magnificent and awe-inspiring, it's impossible for us to resist the mystery of how they came to be."
While all the giant planets in our solar system (Jupiter, Saturn, Uranus and Neptune) have ring systems of their own, Saturn's are clearly different. Explaining why Saturn's rings are so bright and vast is an important challenge in understanding their formation and history. For scientists, the density of material packed into each section of the rings is a critical factor in ascribing their formation to a physical process.
An earlier study by members of Cassini's composite infrared spectrometer team had suggested the possibility that there might be less material in the B ring than researchers had thought. The new analysis is the first to directly measure the density of mass in the ring and demonstrate that this is the case.
Hedman and Nicholson used a new technique to analyze data from a series of observations by Cassini's visible and infrared mapping spectrometer as it peered through the rings toward a bright star. By combining multiple observations, they were able to identify spiral density waves in the rings that aren't obvious in individual measurements.
The analysis also found that the overall mass of the B ring is unexpectedly low. It was surprising, said Hedman, because some parts of the B ring are up to 10 times more opaque than the neighboring A ring, but the B ring may weigh in at only two to three times the A ring's mass.
Despite the low mass found by Hedman and Nicholson, the B ring is still thought to contain the bulk of material in Saturn's ring system. And although this study leaves some uncertainty about the ring's mass, a more precise measurement of the total mass of Saturn's rings is on the way. Previously, Cassini had measured Saturn's gravity field, telling scientists the total mass of Saturn and its rings. In 2017, Cassini will determine the mass of Saturn alone by flying just inside the rings during the final phase of its mission. The difference between the two measurements is expected to finally reveal the rings' true mass.
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New Animation Takes a Colorful Flight Over Ceres (NASA)
A colorful new animation shows a simulated flight over the surface of dwarf planet Ceres, based on images from NASA's Dawn spacecraft.
The movie shows Ceres in enhanced color, which helps to highlight subtle differences in the appearance of surface materials. Scientists believe areas with shades of blue contain younger, fresher material, including flows, pits and cracks.
The animated flight over Ceres emphasizes the most prominent craters, such as Occator, and the tall, conical mountain Ahuna Mons. Features on Ceres are named for earthly agricultural spirits, deities and festivals.
Galaxy Clusters Reveal New Dark Matter Insights (NASA)
Dark matter is a mysterious cosmic phenomenon that accounts for 27 percent of all matter and energy. Though dark matter is all around us, we cannot see it or feel it. But scientists can infer the presence of dark matter by looking at how normal matter behaves around it.
Galaxy clusters, which consist of thousands of galaxies, are important for exploring dark matter because they reside in a region where such matter is much denser than average. Scientists believe that the heavier a cluster is, the more dark matter it has in its environment. But new research suggests the connection is more complicated than that.
"Galaxy clusters are like the large cities of our universe. In the same way that you can look at the lights of a city at night from a plane and infer its size, these clusters give us a sense of the distribution of the dark matter that we can't see," said Hironao Miyatake at NASA's Jet Propulsion Laboratory, Pasadena, California.
A new study in Physical Review Letters, led by Miyatake, suggests that the internal structure of a galaxy cluster is linked to the dark matter environment surrounding it. This is the first time that a property besides the mass of a cluster has been shown to be associated with surrounding dark matter.
Researchers studied approximately 9,000 galaxy clusters from the Sloan Digital Sky Survey DR8 galaxy catalog, and divided them into two groups by their internal structures: one in which the individual galaxies within clusters were more spread out, and one in which they were closely packed together. The scientists used a technique called gravitational lensing -- looking at how the gravity of clusters bends light from other objects -- to confirm that both groups had similar masses.
But when the researchers compared the two groups, they found an important difference in the distribution of galaxy clusters. Normally, galaxy clusters are separated from other clusters by 100 million light-years on average. But for the group of clusters with closely packed galaxies, there were fewer neighboring clusters at this distance than for the sparser clusters. In other words, the surrounding dark-matter environment determines how packed a cluster is with galaxies.
"This difference is a result of the different dark-matter environments in which the groups of clusters formed. Our results indicate that the connection between a galaxy cluster and surrounding dark matter is not characterized solely by cluster mass, but also its formation history," Miyatake said.
Study co-author David Spergel, professor of astronomy at Princeton University in New Jersey, added, "Previous observational studies had shown that the cluster's mass is the most important factor in determining its global properties. Our work has shown that 'age matters': Younger clusters live in different large-scale dark-matter environments than older clusters."
The results are in line with predictions from the leading theory about the origins of our universe. After an event called cosmic inflation, a period of less than a trillionth of a second after the big bang, there were small changes in the energy of space called quantum fluctuations. These changes then triggered a non-uniform distribution of matter. Scientists say the galaxy clusters we see today have resulted from fluctuations in the density of matter in the early universe.
"The connection between the internal structure of galaxy clusters and the distribution of surrounding dark matter is a consequence of the nature of the initial density fluctuations established before the universe was even one second old," Miyatake said.
Researchers will continue to explore these connections.
"Galaxy clusters are remarkable windows into the mysteries of the universe. By studying them, we can learn more about the evolution of large-scale structure of the universe, and its early history, as well as dark matter and dark energy," Miyatake said.
Galaxy clusters, which consist of thousands of galaxies, are important for exploring dark matter because they reside in a region where such matter is much denser than average. Scientists believe that the heavier a cluster is, the more dark matter it has in its environment. But new research suggests the connection is more complicated than that.
"Galaxy clusters are like the large cities of our universe. In the same way that you can look at the lights of a city at night from a plane and infer its size, these clusters give us a sense of the distribution of the dark matter that we can't see," said Hironao Miyatake at NASA's Jet Propulsion Laboratory, Pasadena, California.
A new study in Physical Review Letters, led by Miyatake, suggests that the internal structure of a galaxy cluster is linked to the dark matter environment surrounding it. This is the first time that a property besides the mass of a cluster has been shown to be associated with surrounding dark matter.
Researchers studied approximately 9,000 galaxy clusters from the Sloan Digital Sky Survey DR8 galaxy catalog, and divided them into two groups by their internal structures: one in which the individual galaxies within clusters were more spread out, and one in which they were closely packed together. The scientists used a technique called gravitational lensing -- looking at how the gravity of clusters bends light from other objects -- to confirm that both groups had similar masses.
But when the researchers compared the two groups, they found an important difference in the distribution of galaxy clusters. Normally, galaxy clusters are separated from other clusters by 100 million light-years on average. But for the group of clusters with closely packed galaxies, there were fewer neighboring clusters at this distance than for the sparser clusters. In other words, the surrounding dark-matter environment determines how packed a cluster is with galaxies.
"This difference is a result of the different dark-matter environments in which the groups of clusters formed. Our results indicate that the connection between a galaxy cluster and surrounding dark matter is not characterized solely by cluster mass, but also its formation history," Miyatake said.
Study co-author David Spergel, professor of astronomy at Princeton University in New Jersey, added, "Previous observational studies had shown that the cluster's mass is the most important factor in determining its global properties. Our work has shown that 'age matters': Younger clusters live in different large-scale dark-matter environments than older clusters."
The results are in line with predictions from the leading theory about the origins of our universe. After an event called cosmic inflation, a period of less than a trillionth of a second after the big bang, there were small changes in the energy of space called quantum fluctuations. These changes then triggered a non-uniform distribution of matter. Scientists say the galaxy clusters we see today have resulted from fluctuations in the density of matter in the early universe.
"The connection between the internal structure of galaxy clusters and the distribution of surrounding dark matter is a consequence of the nature of the initial density fluctuations established before the universe was even one second old," Miyatake said.
Researchers will continue to explore these connections.
"Galaxy clusters are remarkable windows into the mysteries of the universe. By studying them, we can learn more about the evolution of large-scale structure of the universe, and its early history, as well as dark matter and dark energy," Miyatake said.
First glimpse of a black hole being born from a star’s remains (N6946-BH1)
Not too much detail so far but it does appear to have followed supernova light curve.
Link to article on New Scientist Web Site
Link to article on New Scientist Web Site
Thursday 24 March 2016
Most Luminous Galaxy Is Ripping Itself Apart
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.
"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.
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."
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