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Astronomers discover class of strange objects near our galaxy’s enormous black hole
January 15, 2020 /in Box 6, College News, Faculty & Research, Featured Stories /by Evelyn Tokuyama
Orbits of the G objects at the center of our galaxy, with the supermassive black hole indicated with a white cross. Stars, gas and dust are in the background. Photo: Anna Ciurlo, Tuan Do/UCLA Galactic Center Group
Astronomers from UCLA’s Galactic Center Orbits Initiative have discovered a new class of bizarre objects at the center of our galaxy, not far from the supermassive black hole called Sagittarius A*. They published their research in the Jan. 16 issue of the journal Nature.
“These objects look like gas and behave like stars,” said co-author Andrea Ghez, UCLA’s Lauren B. Leichtman and Arthur E. Levine Professor of Astrophysics and director of the UCLA Galactic Center Group.
The new objects look compact most of the time and stretch out when their orbits bring them closest to the black hole. Their orbits range from about 100 to 1,000 years, said lead author Anna Ciurlo, a UCLA postdoctoral researcher.
Ghez’s research group identified an unusual object at the center of our galaxy in 2005, which was later named G1. In 2012, astronomers in Germany made a puzzling discovery of a bizarre object named G2 in the center of the Milky Way that made a close approach to the supermassive black hole in 2014. Ghez and her research team believe that G2 is most likely two stars that had been orbiting the black hole in tandem and merged into an extremely large star, cloaked in unusually thick gas and dust.
“At the time of closest approach, G2 had a really strange signature,” Ghez said. “We had seen it before, but it didn’t look too peculiar until it got close to the black hole and became elongated, and much of its gas was torn apart. It went from being a pretty innocuous object when it was far from the black hole to one that was really stretched out and distorted at its closest approach and lost its outer shell, and now it’s getting more compact again.”
“One of the things that has gotten everyone excited about the G objects is that the stuff that gets pulled off of them by tidal forces as they sweep by the central black hole must inevitably fall into the black hole,” said co-author Mark Morris, UCLA professor of physics and astronomy. “When that happens, it might be able to produce an impressive fireworks show since the material eaten by the black hole will heat up and emit copious radiation before it disappears across the event horizon.”
But are G2 and G1 outliers, or are they part of a larger class of objects? In answer to that question, Ghez’s research group reports the existence of four more objects they are calling G3, G4, G5 and G6. The researchers have determined each of their orbits. While G1 and G2 have similar orbits, the four new objects have very different orbits.
Ghez believes all six objects were binary stars — a system of two stars orbiting each other — that merged because of the strong gravitational force of the supermassive black hole. The merging of two stars takes more than 1 million years to complete, Ghez said.
“Mergers of stars may be happening in the universe more often than we thought, and likely are quite common,” Ghez said. “Black holes may be driving binary stars to merge. It’s possible that many of the stars we’ve been watching and not understanding may be the end product of mergers that are calm now. We are learning how galaxies and black holes evolve. The way binary stars interact with each other and with the black hole is very different from how single stars interact with other single stars and with the black hole.”
Ciurlo noted that while the gas from G2’s outer shell got stretched dramatically, its dust inside the gas did not get stretched much. “Something must have kept it compact and enabled it to survive its encounter with the black hole,” Ciurlo said. “This is evidence for a stellar object inside G2.”
“The unique dataset that Professor Ghez’s group has gathered during more than 20 years is what allowed us to make this discovery,” Ciurlo said. “We now have a population of ‘G’ objects, so it is not a matter of explaining a ‘one-time event’ like G2.”
The researchers made observations from the W.M. Keck Observatory in Hawaii and used a powerful technology that Ghez helped pioneer, called adaptive optics, which corrects the distorting effects of the Earth’s atmosphere in real time. They conducted a new analysis of 13 years of their UCLA Galactic Center Orbits Initiative data.
In September 2019, Ghez’s team reported that the black hole is getting hungrier and it is unclear why. The stretching of G2 in 2014 appeared to pull off gas that may recently have been swallowed by the black hole, said co-author Tuan Do, a UCLA research scientist and deputy director of the Galactic Center Group. The mergers of stars could feed the black hole.
The team has already identified a few other candidates that may be part of this new class of objects, and are continuing to analyze them.
Ghez noted the center of the Milky Way galaxy is an extreme environment, unlike our less hectic corner of the universe.
“The Earth is in the suburbs compared to the center of the galaxy, which is some 26,000 light-years away,” Ghez said. “The center of our galaxy has a density of stars 1 billion times higher than our part of the galaxy. The gravitational pull is so much stronger. The magnetic fields are more extreme. The center of the galaxy is where extreme astrophysics occurs — the X-sports of astrophysics.”
Ghez said this research will help to teach us what is happening in the majority of galaxies.
Other co-authors include Randall Campbell, an astronomer with the W.M. Keck Observatory in Hawaii; Aurelien Hees, a former UCLA postdoctoral scholar, now a researcher at the Paris Observatory in France; and Smadar Naoz, a UCLA assistant professor of physics and astronomy.
The research is funded by the National Science Foundation, W.M. Keck Foundation and Keck Visiting Scholars Program, the Gordon and Betty Moore Foundation, the Heising-Simons Foundation, Lauren Leichtman and Arthur Levine, Jim and Lori Keir, and Howard and Astrid Preston.
In July 2019, Ghez’s research team reported on the most comprehensive test of Einstein’s iconic general theory of relativity near the black hole. They concluded that Einstein’s theory passed the test and is correct, at least for now.
► Watch a four-minute film about Ghez’s research
►View an animation below of the orbits of the G objects, together with the orbits of stars near the supermassive black hole. Credit: Advanced Visualization Lab, National Center for Supercomputing Applications, University of Illinois
This article originally appeared in the UCLA Newsroom.
https://www.college.ucla.edu/wp-content/uploads/2020/01/Astronomyimage_edit.jpg 754 1200 Evelyn Tokuyama https://www.college.ucla.edu/wp-content/uploads/2019/07/Uxd_Blk_College-e1557344896161.png Evelyn Tokuyama2020-01-15 14:42:472020-01-15 14:42:47Astronomers discover class of strange objects near our galaxy’s enormous black hole
That Supermassive Black Hole in our Galaxy? It has a Friend.
January 9, 2020 /in Box 3, College News, Faculty & Research, Featured Stories /by Chris Ibarra
Two black holes are entwined in a gravitational tango in this artist’s conception. Photo Credit: NASA/JPL-Caltech/SwRI/MSSS/Christopher Go
Smadar Naoz is an associate professor of physics and astronomy in the UCLA College. She wrote this article for The Conversation.
Do supermassive black holes have friends? The nature of galaxy formation suggests that the answer is yes, and in fact, pairs of supermassive black holes should be common in the universe.
I am an astrophysicist and am interested in a wide range of theoretical problems in astrophysics, from the formation of the very first galaxies to the gravitational interactions of black holes, stars and even planets. Black holes are intriguing systems, and supermassive black holes and the dense stellar environments that surround them represent one of the most extreme places in our universe.
The supermassive black hole that lurks at the center of our galaxy, called Sgr A*, has a mass of about 4 million times that of our sun. A black hole is a place in space where gravity is so strong that neither particles or light can escape from it. Surrounding Sgr A* is a dense cluster of stars. Precise measurements of the orbits of these stars allowed astronomers to confirm the existence of this supermassive black hole and to measure its mass. For more than 20 years, scientists have been monitoring the orbits of these stars around the supermassive black hole. Based on what we’ve seen, my colleagues and I show that if there is a friend there, it might be a second black hole nearby that is at least 100,000 times the mass of the sun.
Supermassive black holes and their friends
Almost every galaxy, including our Milky Way, has a supermassive black hole at its heart, with masses of millions to billions of times the mass of the sun. Astronomers are still studying why the heart of galaxies often hosts a supermassive black hole. One popular idea connects to the possibility that supermassive holes have friends.
To understand this idea, we need to go back to when the universe was about 100 million years old, to the era of the very first galaxies. They were much smaller than today’s galaxies, about 10,000 or more times less massive than the Milky Way. Within these early galaxies the very first stars that died created black holes, of about tens to thousand the mass of the sun. These black holes sank to the center of gravity, the heart of their host galaxy. Since galaxies evolve by merging and colliding with one another, collisions between galaxies will result in supermassive black hole pairs – the key part of this story. The black holes then collide and grow in size as well. A black hole that is more than a million times the mass of our sun is considered supermassive.
If indeed the supermassive black hole has a friend revolving around it in close orbit, the center of the galaxy is locked in a complex dance. The partners’ gravitational tugs will also exert its own pull on the nearby stars disturbing their orbits. The two supermassive black holes are orbiting each other, and at the same time, each is exerting its own pull on the stars around it.
The gravitational forces from the black holes pull on these stars and make them change their orbit; in other words, after one revolution around the supermassive black hole pair, a star will not go exactly back to the point at which it began.
Using our understanding of the gravitational interaction between the possible supermassive black hole pair and the surrounding stars, astronomers can predict what will happen to stars. Astrophysicists like my colleagues and me can compare our predictions to observations, and then can determine the possible orbits of stars and figure out whether the supermassive black hole has a companion that is exerting gravitational influence.
Using a well-studied star, called S0-2, which orbits the supermassive black hole that lies at the center of the galaxy every 16 years, we can already rule out the idea that there is a second supermassive black hole with mass above 100,000 times the mass of the sun and farther than about 200 times the distance between the sun and the Earth. If there was such a companion, then I and my colleagues would have detected its effects on the orbit of SO-2.
But that doesn’t mean that a smaller companion black hole cannot still hide there. Such an object may not alter the orbit of SO-2 in a way we can easily measure.
The physics of supermassive black holes
Supermassive black holes have gotten a lot of attention lately. In particular, the recent image of such a giant at the center of the galaxy M87 opened a new window to understanding the physics behind black holes.
The proximity of the Milky Way’s galactic center – a mere 24,000 light-years away – provides a unique laboratory for addressing issues in the fundamental physics of supermassive black holes. For example, astrophysicists like myself would like to understand their impact on the central regions of galaxies and their role in galaxy formation and evolution. The detection of a pair of supermassive black holes in the galactic center would indicate that the Milky Way merged with another, possibly small, galaxy at some time in the past.
That’s not all that monitoring the surrounding stars can tell us. Measurements of the star S0-2 allowed scientists to carry out a unique test of Einstein’s general theory of relativity. In May 2018, S0-2 zoomed past the supermassive black hole at a distance of only about 130 times the Earth’s distance from the sun. According to Einstein’s theory, the wavelength of light emitted by the star should stretch as it climbs from the deep gravitational well of the supermassive black hole.
The stretching wavelength that Einstein predicted – which makes the star appear redder – was detected and proves that the theory of general relativity accurately describes the physics in this extreme gravitational zone. I am eagerly awaiting the second closest approach of S0-2, which will occur in about 16 years, because astrophysicists like myself will be able to test more of Einstein’s predictions about general relativity, including the change of the orientation of the stars’ elongated orbit. But if the supermassive black hole has a partner, this could alter the expected result.
Finally, if there are two massive black holes orbiting each other at the galactic center, as my team suggests is possible, they will emit gravitational waves. Since 2015, the LIGO-Virgo observatories have been detecting gravitational wave radiation from merging stellar-mass black holes and neutron stars. These groundbreaking detections have opened a new way for scientists to sense the universe.
Any waves emitted by our hypothetical black hole pair will be at low frequencies, too low for the LIGO-Virgo detectors to sense. But a planned space-based detector known as LISA may be able to detect these waves which will help astrophysicists figure out whether our galactic center black hole is alone or has a partner.
https://www.college.ucla.edu/wp-content/uploads/2020/01/twinblackholesillo_7a411b7a-519f-4bab-a545-c0e75c8440ef-prv.jpg 675 1200 Chris Ibarra https://www.college.ucla.edu/wp-content/uploads/2019/07/Uxd_Blk_College-e1557344896161.png Chris Ibarra2020-01-09 13:42:332020-01-09 13:42:33That Supermassive Black Hole in our Galaxy? It has a Friend.
New NASA image provides more details about first observed interstellar comet
December 19, 2019 /in Box 3, College News, Faculty & Research /by Chris Ibarra
The interstellar comet Comet 2I/Borisov (blueish image at right) near a spiral galaxy (left), in an image taken Nov. 16. Photo credit: NASA, ESA and David Jewitt/UCLA
A new image from NASA’s Hubble Space Telescope provides important new details about the first interstellar comet astronomers have seen in our solar system.
The comet, called Comet 2I/Borisov (the “I” stands for interstellar), was spotted near a spiral galaxy known as 2MASX J10500165-0152029. It was approximately 203 million miles from Earth when the image was taken on Nov. 16.
“Data from the Hubble Space Telescope give us the best measure of the size of comet 2I/Borisov’s nucleus, which is the really important part of the comet,” said David Jewitt, a UCLA professor of planetary science and astronomy who analyzed and interpreted the data from the new image.
Jewitt collaborated on the new analysis with colleagues from the University of Hawaii, Germany’s Max Planck Institute for Solar System Research, the Space Telescope Science Institute in Baltimore and Johns Hopkins University’s Applied Physics Laboratory. The scientists were surprised to learn that the nucleus has a radius measuring only about half of a kilometer — or less than one-fifteenth the size that earlier investigations suggested it might be.
“That is important because knowing its size helps us to determine the total number, and mass, of other similar objects in the solar system and the Milky Way,” Jewitt said. “2I/Borisov is the first known interstellar comet, and we would like to learn how many others there are.”
The comet is traveling at a breathtaking speed of 110,000 miles per hour — one of the fastest comets ever seen, Jewitt said. More commonly, comets travel at about half that speed.
Crimean astronomer Gennady Borisov discovered the comet on Aug. 30, using a telescope he built. Based on precise measurements of its changing position, the International Astronomical Union’s Minor Planet Center calculated a likely orbit for the comet, which shows that it came from elsewhere in the galaxy. Jewitt said its precise point of origin is unknown.
A second Hubble Space Telescope image of the comet, taken on Dec. 9, shows the comet even closer to Earth, approximately 185 million miles from Earth, he said.
Comets are icy bodies thought to be fragments left behind when planets form in the outer parts of planetary systems.
Observations by numerous telescopes show that the comet’s chemical composition is similar to that of comets previously observed in our solar system, which provides evidence that comets also form around other stars, Jewitt said. By mid-2020, the comet will have zoomed past Jupiter on its way back into interstellar space, where it will drift for billions of years, Jewitt said.
https://www.college.ucla.edu/wp-content/uploads/2019/12/InterstellarcometNov16_33dd2801-34f4-4749-afbd-40adcc88c3d0-prv.jpg 833 913 Chris Ibarra https://www.college.ucla.edu/wp-content/uploads/2019/07/Uxd_Blk_College-e1557344896161.png Chris Ibarra2019-12-19 14:30:132019-12-19 14:30:13New NASA image provides more details about first observed interstellar comet
Activist Hindou Oumarou Ibrahim wins Pritzker Award for young environmental innovators
November 15, 2019 /in Box 2 /by Chris Ibarra
Hindou Oumarou Ibrahim reacts to the award announcement as UCLA professor Magali Delmas (left) looks on. Photo: Jonathan Young/UCLA
The UCLA Institute of the Environment and Sustainability presented the 2019 Pritzker Emerging Environmental Genius Award to Hindou Oumarou Ibrahim, a member of Chad’s Mbororo indigenous semi-nomadic community.
Ibrahim promotes environmental protections for indigenous groups through work with international organizations, including as a member of the United Nations Indigenous Peoples Partnership’s policy board. She also leads a community-based environmental coalition in the region surrounding Lake Chad, a critical water source that has shrunk 90% since 1980 — in part because temperatures in the area rose 1.5 degrees Celsius over the past century. Violent conflict has occasionally broken out among groups competing for the vital resource.
The annual award carries a prize of $100,000, which is funded through a portion of a $20 million gift to UCLA from the Anthony and Jeanne Pritzker Family Foundation. It is the field’s first major honor specifically for innovators under the age of 40 — those whose work stands to benefit most from the prize money and the prestige it conveys.
Ibrahim said the award, which was presented Nov. 7 at UCLA’s Hershey Hall, will help amplify the voices of 370 million indigenous people around the world.
“The voices of indigenous people are being heard here — through me, through all of you and through this prize,” Ibrahim said. “We are all together. We will win this battle, I am so confident.”
University researchers, Pentagon experts and others have found that rapid climate change — driven largely by human-caused carbon emissions — have contributed to a growing number of armed conflicts. The phenomenon is expected to particularly affect regions that are already unstable.
To prevent and reduce conflict in the Lake Chad basin, Ibrahim developed a program that gathers information on natural resources from farmers, fisherman and herders in more than a dozen African ethnic groups, and then produces 3D maps of those natural resources that their communities can share. The effort is intended to reduce the chance for conflict among the groups.
“It’s amazing to see women and men who have never been to school working jointly to build 3D maps that share critical knowledge, like where fresh water can be found even in the worst days of a drought,” Ibrahim wrote in her award application. “But the most interesting aspect of this project is that it helps to reduce conflict and tension between communities.”
Hindou is an official adviser to the UN Secretary General in advance of a major climate summit taking place in Glasgow in September 2020. She also advocates for indigenous peoples’ rights, women’s rights and environmental justice in high-profile global forums, including as a National Geographic Explorer and a senior indigenous fellow for Conservation International.
Shawn Escoffery, executive director of the Roy and Patricia Disney Foundation, with the 2019 Pritzker Award finalists, May Boeve, Hindou Oumarou Ibrahim and Varshini Prakash. Photo: Jonathan Young/UCLA
The Pritzker Award is open to anyone working to solve environmental challenges through any lens — from science to advocacy and entrepreneurism. But all three finalists for this year’s award were activists, which may reflect the global trend of young people taking a more vigorous role in fighting against climate change. In addition to Ibrahim, the finalists were May Boeve, executive director of 350.org, and Varshini Prakash, founder of the Sunrise Movement. Finalists were selected by a panel of UCLA faculty from 20 candidates who were nominated by an international group of environmental leaders.
Ibrahim was chosen as winner by five distinguished judges: Shawn Escoffery, executive director of the Roy and Patricia Disney Foundation; sustainability and marketing expert Geof Rochester; philanthropists Wendy Schmidt and Nicolas Berggruen; and Kathryn Sullivan, former head of the National Oceanic and Atmospheric Administration and the first American woman to walk in space.
Peter Kareiva, director of UCLA Institute of the Environment and Sustainability, said the Pritzker Award’s biggest value is that it brings together a community of candidates, past winners, UCLA faculty and the environmental leaders who serve as judges and nominators.
“We’re way beyond the time where a single innovation is going to do it, a single policy is going to do it. We’re way beyond that,” Kareiva said.
After receiving the award from Tony Pritzker, Ibrahim echoed that sentiment and called the other finalists up to the podium.
“We need action, and this action can only happen if we all join hands,” Ibrahim said. “We will make it all together.”
https://www.college.ucla.edu/wp-content/uploads/2019/11/HindouOumarouIbrahimreactstoaward_dfe43cc6-27fa-4582-bd92-5d60d9af270d-prv.jpg 800 1200 Chris Ibarra https://www.college.ucla.edu/wp-content/uploads/2019/07/Uxd_Blk_College-e1557344896161.png Chris Ibarra2019-11-15 15:04:302019-11-15 15:04:30Activist Hindou Oumarou Ibrahim wins Pritzker Award for young environmental innovators
UCLA astronomer gets best look at first comet from outside our solar system
October 17, 2019 /in Box 4 /by Chris Ibarra
The comet 2I/Borisov, as seen on Oct. 12 with NASA’s Hubble Space Telescope. Scientists believe the comet is from another solar system. Photo credit: NASA, ESA and David Jewitt/UCLA
David Jewitt, a UCLA professor of planetary science and astronomy, has captured the best and sharpest look at a comet from outside of our solar system that recently barged into our own. It is the first interstellar comet astronomers have observed.
Comet 2I/Borisov (the “I” stands for interstellar) is following a path around the sun at a blazing speed of approximately 110,000 miles per hour, or about as fast as Earth travels around the sun. Jewitt studied it on Oct. 12 using NASA’s Hubble Space Telescope, which captured images of the object when it was about 260 million miles away. He observed a central concentration of dust around the comet’s solid icy nucleus — the nucleus itself is too small to be seen by Hubble — with a 100,000-mile-long dust tail streaming behind.
Jewitt said it’s very different from another interstellar object, dubbed ‘Oumuamua, that a University of Hawaii astronomer observed in 2017 before it raced out of our solar system.
“‘Oumuamua looked like a bare rock, but Borisov is really active — more like a normal comet,” said Jewitt, who leads the Hubble team. “It’s a puzzle why these two are so different. There is so much dust on this thing we’ll have to work hard to dig out the nucleus.”
That work will involve sophisticated image processing to separate the light scattered from the nucleus from light scattered by dust.
► View a 2-second time lapse video of the comet
2I/Borisov and ‘Oumuamua are the first two objects that have traveled from outside of our solar system into ours that astronomers have observed, but that’s because scientists’ knowledge and equipment are much better now than they ever have been, and because they know how to find them. One study indicates there are thousands of such comets in our solar system at any given time, although most are too faint to be detected with current telescopes.
Until 2I/Borisov, every comet that astronomers have observed originated from one of two places. One is the Kuiper belt, a region at the periphery of our solar system, beyond Neptune, that Jewitt co-discovered in 1992. The other is the Oort Cloud, a very large spherical region approximately a light-year from the sun, which astronomers think contains hundreds of billions of comets.
2I/Borisov was initially detected on Aug. 30 by Gennady Borisov at the Crimean Astrophysical Observatory, when it was 300 million miles from the sun. Jewitt said its unusually fast speed — too fast for the sun’s gravity to keep it bound in an orbit — indicates that it came from another solar system and that it is on a long path en route back to its home solar system.
Because the comet was presumably forged in a distant solar system, the comet provides valuable clues about the chemical composition and structure of the system where it originated.
2I/Borisov will be visible in the southern sky for several months. It will make its closest approach to the sun on Dec. 7, when it will be twice as far from the sun as Earth is. By the middle of 2020, it will pass Jupiter on its way back into interstellar space, where it will drift for billions of years, Jewitt said.
20 new moons for Saturn
In separate research that has not yet been published, Jewitt is part of a team that has identified 20 previously undiscovered moons of Saturn, for a new total of 82 moons. The revised figure gives Saturn more moons than Jupiter, which has 79.
The new objects are all small, typically a few miles in diameter, and were discovered using the Subaru telescope on Maunakea in Hawaii. They can be seen only using the world’s largest telescopes, Jewitt said.
The moons might have formed in the Kuiper belt, said Jewitt, a member of the National Academy of Sciences and a fellow of the American Association for the Advancement of Science and of the American Academy of Arts and Sciences.
The research team was headed by Scott Sheppard, a staff scientist at the Carnegie Institution for Science, and includes Jan Kleyna, a postdoctoral scholar at the University of Hawaii.
https://www.college.ucla.edu/wp-content/uploads/2019/10/Interstellarcomet2019_33a5520d-02ea-4585-97c4-a3db760d1efa-prv.jpg 1200 1200 Chris Ibarra https://www.college.ucla.edu/wp-content/uploads/2019/07/Uxd_Blk_College-e1557344896161.png Chris Ibarra2019-10-17 15:33:492019-10-17 15:33:49UCLA astronomer gets best look at first comet from outside our solar system
Black hole at the center of our galaxy appears to be getting hungrier
September 30, 2019 /in College News, Faculty & Research /by Chris Ibarra
Rendering of a star called S0-2 orbiting the supermassive black hole at the center of the Milky Way. It did not fall in, but its close approach could be one reason for the black hole’s growing appetite. Photo credit: Nicolle Fuller/National Science Foundation
The enormous black hole at the center of our galaxy is having an unusually large meal of interstellar gas and dust, and researchers don’t yet understand why.
“We have never seen anything like this in the 24 years we have studied the supermassive black hole,” said Andrea Ghez, UCLA professor of physics and astronomy and a co-senior author of the research. “It’s usually a pretty quiet, wimpy black hole on a diet. We don’t know what is driving this big feast.”
A paper about the study, led by the UCLA Galactic Center Group, which Ghez heads, is published today in Astrophysical Journal Letters.
The researchers analyzed more than 13,000 observations of the black hole from 133 nights since 2003. The images were gathered by the W.M. Keck Observatory in Hawaii and the European Southern Observatory’s Very Large Telescope in Chile. The team found that on May 13, the area just outside the black hole’s “point of no return” (so called because once matter enters, it can never escape) was twice as bright as the next-brightest observation.
They also observed large changes on two other nights this year; all three of those changes were “unprecedented,” Ghez said.
The brightness the scientists observed is caused by radiation from gas and dust falling into the black hole; the findings prompted them to ask whether this was an extraordinary singular event or a precursor to significantly increased activity.
“The big question is whether the black hole is entering a new phase — for example if the spigot has been turned up and the rate of gas falling down the black hole ‘drain’ has increased for an extended period — or whether we have just seen the fireworks from a few unusual blobs of gas falling in,” said Mark Morris, UCLA professor of physics and astronomy and the paper’s co-senior author.
The team has continued to observe the area and will try to settle that question based on what they see from new images.
“We want to know how black holes grow and affect the evolution of galaxies and the universe,” said Ghez, UCLA’s Lauren B. Leichtman and Arthur E. Levine Professor of Astrophysics. “We want to know why the supermassive hole gets brighter and how it gets brighter.”
► UCLA astronomers discussed the project in a Keck Observatory video
The new findings are based on observations of the black hole — which is called Sagittarius A*, or Sgr A* — during four nights in April and May at the Keck Observatory. The brightness surrounding the black hole always varies somewhat, but the scientists were stunned by the extreme variations in brightness during that timeframe, including their observations on May 13.
“The first image I saw that night, the black hole was so bright I initially mistook it for the star S0-2, because I had never seen Sagittarius A* that bright,” said UCLA research scientist Tuan Do, the study’s lead author. “But it quickly became clear the source had to be the black hole, which was really exciting.”
One hypothesis about the increased activity is that when a star called S0-2 made its closest approach to the black hole during the summer 2018, it launched a large quantity of gas that reached the black hole this year.
Another possibility involves a bizarre object known as G2, which is most likely a pair of binary stars, which made its closest approach to the black hole in 2014. It’s possible the black hole could have stripped off the outer layer of G2, Ghez said, which could help explain the increased brightness just outside the black hole.
Morris said another possibility is that the brightening corresponds to the demise of large asteroids that have been drawn in to the black hole.
No danger to Earth
The black hole is some 26,000 light-years away and poses no danger to our planet. Do said the radiation would have to be 10 billion times as bright as what the astronomers detected to affect life on Earth.
Astrophysical Journal Letters also published a second article by the researchers, describing speckle holography, the technique that enabled them to extract and use very faint information from 24 years of data they recorded from near the black hole.
Ghez’s research team reported July 25 in the journal Science the most comprehensive test of Einstein’s iconic general theory of relativity near the black hole. Their conclusion that Einstein’s theory passed the test and is correct, at least for now, was based on their study of S0-2 as it made a complete orbit around the black hole.
Ghez’s team studies more than 3,000 stars that orbit the supermassive black hole. Since 2004, the scientists have used a powerful technology that Ghez helped pioneer, called adaptive optics, which corrects the distorting effects of the Earth’s atmosphere in real time. But speckle holography enabled the researchers to improve the data from the decade before adaptive optics came into play. Reanalyzing data from those years helped the team conclude that they had not seen that level of brightness near the black hole in 24 years.
“It was like doing LASIK surgery on our early images,” Ghez said. “We collected the data to answer one question and serendipitously unveiled other exciting scientific discoveries that we didn’t anticipate.”
Co-authors include Gunther Witzel, a former UCLA research scientist currently at Germany’s Max Planck Institute for Radio Astronomy; Mark Morris, UCLA professor of physics and astronomy; Eric Becklin, UCLA professor emeritus of physics and astronomy; Rainer Schoedel, a researcher at Spain’s Instituto de Astrofısica de Andalucıa; and UCLA graduate students Zhuo Chen and Abhimat Gautam.
The research is funded by the National Science Foundation, W.M. Keck Foundation, the Gordon and Betty Moore Foundation, the Heising-Simons Foundation, Lauren Leichtman and Arthur Levine, and Howard and Astrid Preston.
https://www.college.ucla.edu/wp-content/uploads/2019/09/AndreaGhezblackholeartbyNicolleFullerfinal2019_3f356069-a011-4b89-8983-b3cb3ea118b6-prv.jpg 860 1200 Chris Ibarra https://www.college.ucla.edu/wp-content/uploads/2019/07/Uxd_Blk_College-e1557344896161.png Chris Ibarra2019-09-30 09:52:372019-09-30 09:53:12Black hole at the center of our galaxy appears to be getting hungrier
Einstein’s general relativity theory is questioned but still stands ‘for now,’ team reports
July 25, 2019 /in Faculty & Research, Featured Stories /by Stuart Wolpert
A star known as S0-2 (the blue and green object in this artist’s rendering) made its closest approach to the supermassive black hole at the center of the Milky Way in 2018. Artist’s rendering by Nicolle Fuller/National Science Foundation.
More than 100 years after Albert Einstein published his iconic theory of general relativity, it is beginning to fray at the edges, said Andrea Ghez, UCLA professor of physics and astronomy. Now, in the most comprehensive test of general relativity near the monstrous black hole at the center of our galaxy, Ghez and her research team report July 25 in the journal Science that Einstein’s theory of general relativity holds up.
“Einstein’s right, at least for now,” said Ghez, a co-lead author of the research. “We can absolutely rule out Newton’s law of gravity. Our observations are consistent with Einstein’s theory of general relativity. However, his theory is definitely showing vulnerability. It cannot fully explain gravity inside a black hole, and at some point we will need to move beyond Einstein’s theory to a more comprehensive theory of gravity that explains what a black hole is.”
Einstein’s 1915 theory of general relativity holds that what we perceive as the force of gravity arises from the curvature of space and time. The scientist proposed that objects such as the sun and the Earth change this geometry. Einstein’s theory is the best description of how gravity works, said Ghez, whose UCLA-led team of astronomers has made direct measurements of the phenomenon near a supermassive black hole — research Ghez describes as “extreme astrophysics.”
The laws of physics, including gravity, should be valid everywhere in the universe, said Ghez, who added that her research team is one of only two groups in the world to watch a star known as S0-2 make a complete orbit in three dimensions around the supermassive black hole at the center of the Milky Way. The full orbit takes 16 years, and the black hole’s mass is about 4 million times that of the sun.
The researchers say their work is the most detailed study ever conducted into the supermassive black hole and Einstein’s theory of general relativity.
The key data in the research were spectra that Ghez’s team analyzed last April, May and September as her “favorite star” made its closest approach to the enormous black hole. Spectra, which Ghez described as the “rainbow of light” from stars, show the intensity of light and offer important information about the star from which the light travels. Spectra also show the composition of the star. These data were combined with measurements Ghez and her team have made over the last 24 years.
Spectra — collected at the W.M. Keck Observatory in Hawaii using a spectrograph built at UCLA by a team led by colleague James Larkin — provide the third dimension, revealing the star’s motion at a level of precision not previously attained. (Images of the star the researchers took at the Keck Observatory provide the two other dimensions.) Larkin’s instrument takes light from a star and disperses it, similar to the way raindrops disperse light from the sun to create a rainbow, Ghez said.
“What’s so special about S0-2 is we have its complete orbit in three dimensions,” said Ghez, who holds the Lauren B. Leichtman and Arthur E. Levine Chair in Astrophysics. “That’s what gives us the entry ticket into the tests of general relativity. We asked how gravity behaves near a supermassive black hole and whether Einstein’s theory is telling us the full story. Seeing stars go through their complete orbit provides the first opportunity to test fundamental physics using the motions of these stars.”
Ghez’s research team was able to see the co-mingling of space and time near the supermassive black hole. “In Newton’s version of gravity, space and time are separate, and do not co-mingle; under Einstein, they get completely co-mingled near a black hole,” she said.
“Making a measurement of such fundamental importance has required years of patient observing, enabled by state-of-the-art technology,” said Richard Green, director of the National Science Foundation’s division of astronomical sciences. For more than two decades, the division has supported Ghez, along with several of the technical elements critical to the research team’s discovery. “Through their rigorous efforts, Ghez and her collaborators have produced a high-significance validation of Einstein’s idea about strong gravity.”
Keck Observatory Director Hilton Lewis called Ghez “one of our most passionate and tenacious Keck users.” “Her latest groundbreaking research,” he said, “is the culmination of unwavering commitment over the past two decades to unlock the mysteries of the supermassive black hole at the center of our Milky Way galaxy.”
The researchers studied photons — particles of light — as they traveled from S0-2 to Earth. S0-2 moves around the black hole at blistering speeds of more than 16 million miles per hour at its closest approach. Einstein had reported that in this region close to the black hole, photons have to do extra work. Their wavelength as they leave the star depends not only on how fast the star is moving, but also on how much energy the photons expend to escape the black hole’s powerful gravitational field. Near a black hole, gravity is much stronger than on Earth.
Ghez was given the opportunity to present partial data last summer, but chose not to so that her team could thoroughly analyze the data first. “We’re learning how gravity works. It’s one of four fundamental forces and the one we have tested the least,” she said. “There are many regions where we just haven’t asked, how does gravity work here? It’s easy to be overconfident and there are many ways to misinterpret the data, many ways that small errors can accumulate into significant mistakes, which is why we did not rush our analysis.”
Ghez, a 2008 recipient of the MacArthur “Genius” Fellowship, studies more than 3,000 stars that orbit the supermassive black hole. Hundreds of them are young, she said, in a region where astronomers did not expect to see them.
It takes 26,000 years for the photons from S0-2 to reach Earth. “We’re so excited, and have been preparing for years to make these measurements,” said Ghez, who directs the UCLA Galactic Center Group. “For us, it’s visceral, it’s now — but it actually happened 26,000 years ago!”
This is the first of many tests of general relativity Ghez’s research team will conduct on stars near the supermassive black hole. Among the stars that most interest her is S0-102, which has the shortest orbit, taking 11 1/2 years to complete a full orbit around the black hole. Most of the stars Ghez studies have orbits of much longer than a human lifespan.
Ghez’s team took measurements about every four nights during crucial periods in 2018 using the Keck Observatory — which sits atop Hawaii’s dormant Mauna Kea volcano and houses one of the world’s largest and premier optical and infrared telescopes. Measurements are also taken with an optical-infrared telescope at Gemini Observatory and Subaru Telescope, also in Hawaii. She and her team have used these telescopes both on site in Hawaii and remotely from an observation room in UCLA’s department of physics and astronomy.
Black holes have such high density that nothing can escape their gravitational pull, not even light. (They cannot be seen directly, but their influence on nearby stars is visible and provides a signature. Once something crosses the “event horizon” of a black hole, it will not be able to escape. However, the star S0-2 is still rather far from the event horizon, even at its closest approach, so its photons do not get pulled in.)
Lasers from the two Keck telescopes point in the direction of the center of our galaxy. Each laser creates an “artificial star” that astronomers can use to correct for the blurring caused by the Earth’s atmosphere. Photo: Ethan Tweedie
Ghez’s co-authors include Tuan Do, lead author of the Science paper, a UCLA research scientist and deputy director of the UCLA Galactic Center Group; Aurelien Hees, a former UCLA postdoctoral scholar, now a researcher at the Paris Observatory; Mark Morris, UCLA professor of physics and astronomy; Eric Becklin, UCLA professor emeritus of physics and astronomy; Smadar Naoz, UCLA assistant professor of physics and astronomy; Jessica Lu, a former UCLA graduate student who is now a UC Berkeley assistant professor of astronomy; UCLA graduate student Devin Chu; Greg Martinez, UCLA project scientist; Shoko Sakai, a UCLA research scientist; Shogo Nishiyama, associate professor with Japan’s Miyagi University of Education; and Rainer Schoedel, a researcher with Spain’s Instituto de Astrofısica de Andalucıa.
The National Science Foundation has funded Ghez’s research for the last 25 years. More recently, her research has also been supported by the W.M. Keck Foundation, the Gordon and Betty Moore Foundation and the Heising-Simons Foundation; as well as Lauren Leichtman and Arthur Levine, and Howard and Astrid Preston.
In 1998, Ghez answered one of astronomy’s most important questions, helping to show that a supermassive black hole resides at the center of our Milky Way galaxy. The question had been a subject of much debate among astronomers for more than a quarter of a century.
A powerful technology that Ghez helped to pioneer, called adaptive optics, corrects the distorting effects of the Earth’s atmosphere in real time. With adaptive optics at Keck Observatory, Ghez and her colleagues have revealed many surprises about the environments surrounding supermassive black holes. For example, they discovered young stars where none was expected to be seen and a lack of old stars where many were anticipated. It’s unclear whether S0-2 is young or just masquerading as a young star, Ghez said.
In 2000, she and colleagues reported that for the first time, astronomers had seen stars accelerate around the supermassive black hole. In 2003, Ghez reported that the case for the Milky Way’s black hole had been strengthened substantially and that all of the proposed alternatives could be excluded.
In 2005, Ghez and her colleagues took the first clear picture of the center of the Milky Way, including the area surrounding the black hole, at Keck Observatory. And in 2017, Ghez’s research team reported that S0-2 does not have a companion star, solving another mystery.
https://www.college.ucla.edu/wp-content/uploads/2019/07/Ghez_300x200.jpg 200 300 Stuart Wolpert https://www.college.ucla.edu/wp-content/uploads/2019/07/Uxd_Blk_College-e1557344896161.png Stuart Wolpert2019-07-25 12:13:532019-07-25 12:15:33Einstein’s general relativity theory is questioned but still stands ‘for now,’ team reports
Air quality app influences behavior by linking environment to health
July 22, 2019 /in Faculty & Research, Featured Stories /by UCLA Newsroom
An air quality app prompted a majority of its users to take measures to reduce air pollution’s effects on their health.
Nine out of 10 people worldwide breathe polluted air and 7 million die every year from air pollution, according to the World Health Organization. Air quality mobile applications could mitigate these health risks by educating people and promoting preventive behavioral changes, a UCLA study found.
“I think information can be very powerful to change your behavior,” said the study’s lead author, Magali Delmas, a professor of management at the UCLA Institute of the Environment and Sustainability and the Anderson School of Management.
To test the effectiveness of an air quality app, a team of UCLA researchers created AirForU. Similar to a weather app, AirForU gave users information such as hourly air quality updates, next-day air quality forecasts and seven-day historical averages. Data was taken from the Environmental Protection Agency’s AirNow website.
Sixty-nine percent of the app’s 2,740 users said the app prompted them to take measures to reduce air pollution’s effects on their health, and 58% said they learned new information about the health impacts of air pollution.The researchers tracked how often users checked the app and surveyed them to find out how often they shared air quality information with others.
Engagement was found to be highest among health-conscious users, including those who exercised frequently or had preexisting conditions — such as asthma or heart disease — that can be aggravated by air pollution. These users opened the app one to two more times a week than other users.
Additional motivations such as emails and in-app notifications increased engagement, generating two to three more app visits a week. However, the paper’s authors noted that too many notifications could backfire, annoying users.
As part of an end-of-study feedback survey, researchers measured behavioral changes. The most common actions users took to protect their health were not exercising outdoors when air pollution levels were high (21.7%) and closing windows (20.2%). Their knowledge of air quality rose as well, from 10% in the intake survey to 70% in the exit survey.
The study ran from 2015 to 2017, but it was cut short. “[A] company used lawyers to try to influence the type of information we provided in the app,” the study stated, after “one app user contacted a facility about their toxic releases.” The letter was written by attorneys representing an unidentified company. Though all of the app’s information was publicly available through government sources, UCLA Health decided to remove the app from the store. By that time, the information needed for the study had already been collected.
The researchers suggested increasing transparency about data sourcing and potentially including attorneys in development teams for similar apps.
Maintaining long-term engagement was another challenge. App engagement dropped 90 percent about three months after signup. The paper’s authors suggest it could indicate that users learned enough during that time, or that additional strategies are needed to engage them further.
While users can no longer download AirForU, Delmas and Kohli see potential for future apps to go beyond educating users and promote behavioral change — informing public advocacy to address air pollution through policies and responsible business practices.
“I hope others will learn from what we did to build something that is even more effective,” Delmas said.
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Physical Sciences Dean Miguel García-Garibay has been elected a 2019 Fellow of the American Chemical Society
Miguel García-Garibay, Dean of the UCLA College Division of Physical Sciences.
Miguel García-Garibay, dean of the UCLA Division of Physical Sciences and professor of chemistry and biochemistry, has been elected a 2019 fellow of the American Chemical Society, the ACS announced.
García-Garibay is a pioneer in research on molecular motion in crystals, molecular machines and green chemistry.
He has earned worldwide recognition in the fields of organic photochemistry, solid-state organic chemistry and physical organic chemistry. García-Garibay studies the interaction of light and molecules in crystals. Light can have enough energy to break and make bonds in molecules, and his research team has shown that crystals offer an opportunity to control the outcome of these chemical reactions. He is interested in the basic science of molecules in crystals.
His research has applications for green chemistry that may lead to the production of specialty chemicals that would be very difficult to produce by traditional methods due to their complex structures, as well as applications for molecular electronics and miniaturized devices. His research group has made advances in the field of artificial molecular machines and amphidynamic crystals, a term García-Garibay invented, referring to crystals built with molecules that have a combination of static and mobile components. His research is funded by the National Science Foundation, among other funding sources.
“I can get a precise picture of the molecules in the crystals, the precise arrangement of atoms, with almost no uncertainty,” García-Garibay said. “This provides a large level of control, which enables us to learn the different principles governing molecular functions at the nanoscale.”
He has won many honors for his research, including selection as a fellow of the American Association for the Advancement of Science, as well as numerous honors from the National Science Foundation and the American Chemical Society. He is a member of the California NanoSystems Institute and the Society for Advancement of Chicanos/Hispanics and Native Americans in Science, among other scholarly organizations.
ACS fellows are nominated by their peers and selected for their outstanding accomplishments in scientific research, education and public service. The 2019 fellows will be honored at a ceremony during the ACS national meeting in San Diego on Aug. 26.
This story originally appeared here.
https://www.college.ucla.edu/wp-content/uploads/2019/07/PS_Garibay_300x200.jpg 200 300 Stuart Wolpert https://www.college.ucla.edu/wp-content/uploads/2019/07/Uxd_Blk_College-e1557344896161.png Stuart Wolpert2019-07-17 08:42:022019-07-17 08:42:02Physical Sciences Dean Miguel García-Garibay has been elected a 2019 Fellow of the American Chemical Society
Mathematician named a Great Immigrant by Carnegie Corporation
Terence Tao. Photo Credit: Reed Hutchinson
Terence Tao, professor of mathematics, who holds the James and Carol Collins Chair in the UCLA College, has been named by Carnegie Corporation of New York on its 2019 annual list of Great Immigrants — a salute to 38 naturalized citizens who “strengthen America’s economy, enrich our culture and communities, and invigorate our democracy through their lives, their work, and their examples.”
Tao became the first mathematics professor in UCLA history to be awarded the Fields Medal in 2006, often described as the “Nobel Prize in mathematics.” He has earned many other honors, including the National Science Foundation’s Alan T. Waterman Award, the Breakthrough Prize in Mathematics, Royal Society’s 2014 Royal Medal for physical sciences and the Royal Swedish Academy of Sciences’ Crafoord Prize. National Geographic magazine featured him in its “What makes a genius?” May 2017 issue.
Every Fourth of July since 2006, the Carnegie Corporation of New York has sponsored the public awareness initiative to commemorate the legacy of its founder, Scottish immigrant Andrew Carnegie, who believed strongly in both immigration and citizenship.
“As we celebrate these 38 extraordinary individuals, we are reminded of the legacy of our founder, Andrew Carnegie, who showed the country how immigrants contribute to the great, unfinished story that is America,” said Vartan Gregorian, president of Carnegie Corporation of New York.
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