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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 today in 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.
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Astronaut craves salsa and surf after record 11 months aloft – World News – Castanet.net
After nearly 11 months in orbit, the astronaut holding the record for the longest spaceflight by a woman can’t wait to dig into some salsa and chips, and swim and surf in the Gulf of Mexico.
NASA astronaut Christina Koch told The Associated Press on Tuesday — her 319th consecutive day in space — that taking part in the first all-female spacewalk was the highlight of her mission. She’s been living on the International Space Station since March and returns to Earth on Feb. 6, landing in Kazakhstan with two colleagues aboard a Russian capsule.
Koch said she and fellow NASA astronaut Jessica Meir appreciated that the Oct. 18 spacewalk “could serve as an inspiration for future space explorers.”
“We both drew a lot of inspiration from seeing people that were reflections of ourselves as we were growing up and developing our dreams to become astronauts,” Koch said from the space station. “So to recognize that maybe we could pay that forward and serve the same for those that are up and coming was just such a highlight.”
Koch’s astronaut class of 2013 was split equally between women and men, but NASA’s astronaut corps as a whole is male dominated. Right now, four men and two women are living at the space station.
“Diversity is important, and I think it is something worth fighting for,” said Koch, an electrical engineer who also has a physics degree.
Koch’s 328-day mission will be the second-longest by an American, trailing Scott Kelly’s flight by 12 days. She’s already set a record for the longest single spaceflight by a woman.
She took time out for a pair of news interviews Tuesday, the 34th anniversary of the space shuttle Challenger accident that claimed all seven lives on board.
She said she loves her work — she conducted six spacewalks and tended to science experiments — but she also misses her friends and family.
“If they could visit here, I would continue staying for a very long time,” said Koch, a first-time space flier. “For their sake, I think that it’s probably time to head home.”
Why do chips and salsa top her most-missed food list? Crunchy food like chips are banned on the space station because the crumbs could float away and clog equipment. “I haven’t had chips in about 10 1/2 months,” she explained, “but I have had a fresh apple” thanks to regular cargo deliveries.
Potential satellite collision shows need for active debris removal – SpaceNews
WASHINGTON — Two decades-old defunct spacecraft are in danger of colliding Jan. 29, an event experts argue is more evidence of the need to clean up low Earth orbit.
LeoLabs, a California company that operates a network of ground-based radars that track objects in orbit, announced Jan. 27 that it had identified a potential conjunction, or close approach, between the Infrared Astronomical Satellite (IRAS) and the Gravity Gradient Stabilization Experiment (GGSE) 4 satellite in LEO. The company said there was an approximately 1-in-100 chance that the two satellites would collide at 6:39 p.m. Eastern Jan. 29 an altitude of about 900 kilometers, almost directly above the city of Pittsburgh.
LeoLabs, in an update Jan. 28, revised the probability of a collision downward, to about 1 in 1,000, estimating that the two spacecraft will pass between 13 and 87 meters of each other. Other sources have estimated similar probabilities of a collision between the two objects using other data, such as that from the catalog maintained by the U.S. Air Force.
Neither IRAS, launched in 1983, nor GGSE-4, launched in 1967, are operational today and have the ability to maneuver. While close approaches between debris are not uncommon, the circumstances of this event make it unusual and, to some orbital debris experts, worrying.
“This is a little bit unusual,” said Dan Oltrogge, director of the Center for Space Standards and Innovation at Analytical Graphics, Inc., in a Jan. 28 interview. The two spacecraft are in “counterrotating” orbits, meaning a collision would effectively be head-on, at an estimated relative velocity of 14.9 kilometers per second. That would maximize the energy of any collision.
Moreover, IRAS is a large satellite, with a mass of more than 1,000 kilograms. GGSE-4 — also known as POPPY-5B, a signals intelligence satellite — is much smaller, at 85 kilograms. However, it has a boom 18 meters long that will be perpendicular to the direction of motion. “In this case, that tends to maximize the collision potential,” Oltrogge said.
It may not be clear for hours after closest approach if the two satellites avoided a collision, depending on what assets are available to track them. Even if they miss, though, he said the conjunction should serve as a reminder of the hazards that other large objects, both satellites and upper stages, pose in Earth orbit, and the need to remove them.
“Even if these don’t hit, there will be others that will,” he said. “I think this can serve as a wakeup call for us to look at not only avoiding collisions with active satellites, but also remediating, figuring out how to remove debris in orbit.”
A paper that Oltrogge and others presented at the International Astronautical Congress in October 2019 discussed the risks of such collisions. They modeled the collision of two upper stages in orbit at 981 kilometers, concluding it could create between 3,375 and 12,860 objects at least 5 to 10 centimeters in size, as well as more than 200,000 additional debris objects at least 1 centimeter across dubbed “lethal nontrackable” because they are large enough to damage or destroy a satellite but too small to be tracked.
Another co-author of that paper was Darren McKnight of Centauri, who made similar arguments in a presentation at the Advanced Maui Optical and Space Surveillance Technologies conference in September. He noted that, in May, two rocket bodies that are part of a “cluster” of such objects at an altitude of 850 kilometers passed within 87 meters of each other. “They’re big yellow school buses with no driver,” he said. “If they collide, it would have doubled the catalog population in one event.”
“I would hope that we could take this, and other conjunction events and close approaches, to try and get another look at active debris removal and other remediation techniques,” Oltrogge said of this potential conjunction. “But time will tell.”
Can Alexa save your life? U of A researchers put virtual assistants to the test in new study – CTV News
Could your virtual assistant save your life in an emergency situation? A new study by researchers at the University of Alberta suggests that the technology is not there yet.
According to the researchers, two-thirds of medical emergencies happen at home, and with voice-activated internet searches expected to make up 50 per cent of searches by the end of the year, they wanted to determine if the devices could be counted on to provide life-saving information in an emergency.
“Despite being relatively new, these devices show exciting promise to get first aid information into the hands of people who need it in their homes when they need it the most,” said Matthew Douma, an assistant adjunct professor in critical care medicine, who co-authored the study.
Using 123 questions about 39 first aid topics, including heart attacks, poisoning, nosebleeds and slivers, researchers tested Alexa, Google Home, Siri and Cortana. They analyzed the devices’ answers for accuracy of topic recognition, detection of the severity of the emergency, complexity of the language used, and how closely the advice given fit with accepted first aid treatment guidelines.
“We were hoping to find that the devices would have a better response rate, especially to statements like ‘someone is dying’ and ‘I want to die,’ versus things like ‘I have a sunburn or a sliver,'” said lead author Christopher Picard, a master’s student in the Faculty of Nursing and a clinical educator at Edmonton’s Misericordia Community Hospital emergency department.
“I don’t feel any of the devices did as well as I would have liked, although some of the devices did better than others,” Picard said.
The study found that Google Home performed the best, recognizing 98 per cent of topics accurately and providing advice that matched with Red Cross first aid guidelines 56 per cent of the time.
Alexa recognized 92 per cent of topics, and gave appropriate advice 19 per cent of the time.
The responses from Siri and Cortana were so low that researchers determined that they couldn’t analyze them.
Picard said that most of the responses from the virtual assistants were excerpts from web pages, instead of complete information. Despite that, he feels there’s still some potential.
“If I had a loved one who is facing an emergency situation, I would prefer them to ask the device than to do nothing at all,” Picard said.
He believes that in the future, the devices will improve to a point where they can listen for symptoms such as breathing patterns associated with cardiac arrest and automatically dial 911.
“At best, Alexa and Google might be able to help save a life about half the time,” said Douma. “For now, people should still keep calling 911 but in the future help might be a little closer.”
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