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  • richardmitnick 8:43 pm on December 9, 2016 Permalink | Reply
    Tags: , Astrophysics, , , , , , , Simons Observatory   

    From LBNL: “$40M to Establish New Observatory Probing Early Universe” 

    Berkeley Logo

    Berkeley Lab

    May 12, 2016 [OMG, where has this been?]
    No writer credit found

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    The Simons Array will be located in Chile’s High Atacama Desert, at an elevation of about 17,000 feet. The site currently hosts the Atacama Cosmology Telescope (bowl-shaped structure at upper right) and the Simons Array (the three telescopes at bottom left, center and right). The Simons Observatory will merge these two experiments, add several new telescopes and set the stage for a next-generation experiment. (Credit: University of Pennsylvania)

    The Simons Foundation has given $38.4 million to establish a new astronomy facility in Chile’s Atacama Desert, adding new telescopes and detectors alongside existing instruments in order to boost ongoing studies of the evolution of the universe, from its earliest moments to today. The Heising-Simons Foundation is providing an additional $1.7 million for the project.

    The Simons Observatory is a collaboration among the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab); UC Berkeley; Princeton University; the University of California at San Diego; and University of Pennsylvania, all of which are also providing financial support.

    The observatory will probe the subtle properties of the universe’s first light, known as cosmic microwave background (CMB) radiation.

    CMB per ESA/Planck
    CMB per ESA/Planck

    ESA/Planck
    ESA/Planck

    The observatory will pay particular attention to the polarization, or directional information, in the CMB light to better understand what took place a fraction of a second after the Big Bang. While these events are hidden from view behind the glare of the microwave radiation, the disturbances they caused in the fabric of space-time affected the microwave’s polarization, and scientists hope to work backwards from these measurements to test theories about how the universe came into existence.

    “The Simons Observatory will allow us to peer behind the dust in our galaxy and search for a true signal from the Big Bang,” said Adrian Lee, a physicist at Berkeley Lab, a UC Berkeley physics professor and one of the lead investigators at the observatory.

    A key goal of the project is to detect gravitational waves generated by cosmic inflation, an extraordinarily rapid expansion of space that, according to the most popular cosmological theory, took place in an instant after the Big Bang. These primordial gravitational waves induced a very small but characteristic polarization pattern, called B-mode polarization, in the microwave background radiation that can be detected by telescopes and cameras like those planned for the Simons Observatory.

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    B-mode polarization Image: BICEP2 Collaboration

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    The Milky Way’s galactic plane rises above the Atacama Cosmology Telescope. The Simons Observatory is planned at the same site in Chile’s High Atacama Desert and will merge existing experiments and add new telescopes and detectors. (Credit: Jon Ward/University of Pennsylvania)

    “While patterns that we see in the microwave sky are a picture of the structure of the universe 380,000 years after the Big Bang, we believe that some of these patterns were generated much earlier, by gravitational waves produced in the first moments of the universe’s expansion,” said project spokesperson Mark Devlin, a cosmologist at the University of Pennsylvania who leads the university’s team in the collaboration. “By measuring how the gravitational waves affect electrons and matter 380,000 years after the Big Bang we are observing fossils from the very, very early universe.”

    Lee added, “Once we see the signal of inflation, it will be the beginning of a whole new era of cosmology.” We will then be looking at a time when the energy scale in the universe was a trillion times higher than the energy accessible in any particle accelerator on Earth.

    By measuring how radiation from the early universe changed as it traveled through space to Earth, the observatory also will teach us about the nature of dark energy and dark matter, the properties of neutrinos and how large-scale structure formed as the universe expanded and evolved.

    Primordial gravitational waves

    Princeton ACT new ,  on Cerro Toco in the Atacama Desert in the north of Chile, near the Llano de Chajnantor Observatory.
    Princeton ACT, on Cerro Toco in the Atacama Desert in the north of Chile, near the Llano de Chajnantor Observatory, pictured here, will merge with another set of instruments, the Simons Array, and new telescopes and equipment will be added at the site with the launch of the Simons Observatory project. (Credit: Princeton University)

    Two existing instruments at the site—the Atacama Cosmology Telescope and the Simons Array—are currently measuring this polarization. The foundation funds will merge these two experiments, expand the search and develop new technology for a fourth-stage, next-generation project—dubbed CMB-Stage 4 or CMB-S4—that could conceivably mine all the cosmological information in the cosmic microwave background fluctuations possible from a ground-based observatory.

    LBL The Simons Array in the Atacama in Chile, with the  Atacama Cosmology Telescope
    LBL The Simons Array in the Atacama in Chile, with the Atacama Cosmology Telescope, on Cerro Toco in the Atacama Desert in the north of Chile, near the Llano de Chajnantor Observatory.

    “We are still in the planning stage for CMB-S4, and this is a wonderful opportunity for the foundations to create a seed for the ultimate experiment,” said Akito Kusaka, a Berkeley Lab physicist and one of the lead investigators. “This gets us off to a quick start.”

    The Simons Observatory is designed to be a first step toward CMB-S4. This next-generation experiment builds on years of support from the National Science Foundation (NSF), and the Department of Energy (DOE) Office of Science has announced its intent to participate in CMB-S4, following the recommendation by its particle physics project prioritization panel. Such a project is envisioned to have telescopes at multiple sites and draw together a broad community of experts from the U.S. and abroad. The Atacama site in Chile has already been identified as an excellent location for CMB-S4, and the Simons Foundation funding will help develop it for that role.

    “We are hopeful that CMB-S4 would shed light not only on inflation, but also on the dark elements of the universe: neutrinos and so-called dark energy and dark matter,” Kusaka said. “The nature of these invisible elements is among the biggest questions in particle physics as well.”

    Beyond POLARBEAR

    Experiments at the Chilean site have already paved the way for CMB-S4. A 2012 UC Berkeley-led experiment with participation by Berkeley Lab researchers, called POLARBEAR, used a 3.5-meter telescope at the Chilean site to measure the gravitational-lensing-generated B-mode polarization of the cosmic microwave background radiation.

    POLARBEAR McGill Telescope located in the Atacama Desert of northern Chile in the Antofagasta Region. The POLARBEAR experiment is mounted on the Huan Tran Telescope (HTT) at the James Ax Observatory in the Chajnantor Science Reserve.
    The POLARBEAR experiment is mounted on the Huan Tran Telescope (HTT) at the James Ax Observatory in the Chajnantor Science Reserve.

    Team scientists confirmed in 2014 that the signal was strong enough to allow them eventually to measure the neutrino mass and the evolution of dark energy.

    The recent addition of two more telescopes upgrades POLARBEAR to the Simons Array, which will speed up the mapping of the CMB and improve sky and frequency coverage. The $40 million in new funding will make possible the successor to the Simons Array and the nearby Atacama Cosmology Telescope.

    Current stage-3 experiments for these short-wavelength microwaves, which must be chilled to three-tenths of a degree Kelvin above absolute zero, have about 10,000 pixels, Lee said.

    “We need to make a leap in our technology to pave the way for the 500,000 detectors required for the ultimate experiment,” he said. “We’ll be generating the blueprint for a much more capable telescope.”

    “The generosity of this award is unprecedented in our field, and will enable a major leap in scientific capability,” said Brian Keating, leader of the UC San Diego contingent and current project director. “People are used to thinking about mega- or gigapixel detectors in optical telescopes, but for signals in the microwave range 10,000 pixels is a lot. What we’re trying to do—the real revolution here—is to pave the way to increase our pixels number by more than an order of magnitude.”

    Berkeley Lab and UC Berkeley will contribute $1.25 million in matching funds to the project over the next five years. The $1.7 million contributed by the Heising-Simons Foundation will be devoted to supporting research at Berkeley to improve the microwave detectors and to develop fabrication methods that are more efficient and cheaper, with the goal of boosting the number of detectors in CMB experiments by more than a factor of a 10.

    The site in Chile is located in the Parque Astronómico, which is administered by the Comisión Nacional de Investigación Científica y Tecnológica (CONICYT). Since 1998, U.S. investigators and the NSF have worked with Chilean scientists, the University of Chile, and CONICYT to locate multiple projects at this high, dry site to study the CMB.

    See the full article here .

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  • richardmitnick 1:14 pm on December 8, 2016 Permalink | Reply
    Tags: , Astrophysics, , , , ,   

    From NYT: Women in STEM – “‘The World Sees Me as the One Who Will Find Another Earth’” Sara Seager 

    New York Times

    The New York Times

    DEC. 7, 2016
    Chris Jones

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    Sara Seager

    Like many astrophysicists, Sara Seager sometimes has a problem with her perception of scale. Knowing that there are hundreds of billions of galaxies, and that each might contain hundreds of billions of stars, can make the lives of astrophysicists and even those closest to them seem insignificant. Their work can also, paradoxically, bolster their sense of themselves. Believing that you alone might answer the question “Are we alone?” requires considerable ego. Astrophysicists are forever toggling between feelings of bigness and smallness, of hubris and humility, depending on whether they’re looking out or within.

    One perfect blue-sky fall day, Seager boarded a train in Concord, Mass., on her way to her office at M.I.T. and realized she didn’t have her phone. She couldn’t seem to decide whether this was or wasn’t a big deal. Not having her phone would make the day tricky in some ways, because her sons, 13-year-old Max and 11-year-old Alex, had a soccer game after school, and she would need to coordinate a ride to watch them. She also wanted to be able to find and sit with her best friend, Melissa, who sometimes takes the same train to work. “She’s my best friend, but I know she has other best friends,” Seager said, wanting to make the nature of their relationship clear. She is an admirer of clarity. She also likes absolutes, wide-open spaces and time to think, but not too much time to think. She took out her laptop to see if she could email Melissa. The train’s Wi-Fi was down. She would have to occupy herself on the commute alone.

    Seager’s office is on the 17th floor of M.I.T.’s Green Building, the tallest building in Cambridge, its roof dotted with meteorological and radar equipment. She is a tenured professor of physics and of planetary science, certified a “genius” by the MacArthur Foundation in 2013. Her area of expertise is the relatively new field of exoplanets: planets that orbit stars other than our sun. More particular, she wants to find an Earthlike exoplanet — a rocky planet of reasonable mass that orbits its star within a temperate “Goldilocks zone” that is not too hot or too cold, which would allow water to remain liquid — and determine that there is life on it. That is as simple as her math gets.

    Seager’s office is on the 17th floor of M.I.T.’s Green Building, the tallest building in Cambridge, its roof dotted with meteorological and radar equipment. She is a tenured professor of physics and of planetary science, certified a “genius” by the MacArthur Foundation in 2013. Her area of expertise is the relatively new field of exoplanets: planets that orbit stars other than our sun. More particular, she wants to find an Earthlike exoplanet — a rocky planet of reasonable mass that orbits its star within a temperate “Goldilocks zone” that is not too hot or too cold, which would allow water to remain liquid — and determine that there is life on it. That is as simple as her math gets.

    That means Seager, who is 45, has given herself a very difficult problem to solve, the problem that has always plagued astronomy, which, at its essence, is the study of light: Light wages war with itself. Light pollutes. Light blinds.

    Seager has a commanding view of downtown Boston from her office window. She can sweep her eyes, hazel and intense, all the way from the gold Capitol dome to Fenway Park. When Seager works at night and the Red Sox are in town, she sometimes has to close her curtains, because the ballpark’s white lights are so glaring. And on this morning, after the sun completed its rise, her enviable vista became unbearable. It was searing, and she had to draw her curtains. That’s how light can be the object of her passion and also her enemy. Little lights — exoplanets — are washed out by bigger lights — their stars — the way stars are washed out by our biggest light, the sun. Seager’s challenge is that she has dedicated her life to the search for the smallest lights.

    The vastness of space almost defies conventional measures of distance. Driving the speed limit to Alpha Centauri, the nearest star grouping to the sun, would take 50 million years or so; our fastest current spacecraft would make the trip in a relatively brisk 73,000 years. The next-nearest star is six light-years away. To rocket across our galaxy would take about 23,000 times as long as a trip to Alpha Centauri, or 1.7 billion years, and the Milky Way is just one of hundreds of billions of galaxies. The Hubble Space Telescope once searched a tiny fragment of the night sky, the size of a penny held at arm’s length, that was long thought by astronomers to be dark. It contained 3,000 previously unseen points of light. Not 3,000 new stars — 3,000 new galaxies. And in all those galaxies, orbiting around some large percentage of each of their virtually countless stars: planets. Planets like Neptune, planets like Mercury, planets like Earth.

    As late as the 1990s, exoplanets remained a largely theoretical construct. Logic dictated that they must be out there, but proof of their existence remained as out of reach as they were. Some scientists dismissed efforts to find exoplanets as “stamp collecting,” a derogatory term within the community for hunting new, unreachable lights just to name them. (Even among astronomers, there can be too much stargazing.) It wasn’t until 1995 that the colossal 51 Pegasi b, the first widely recognized exoplanet orbiting a sunlike star, was found by a pair of Swiss astronomers using a light-analyzing spectrograph. The Swiss didn’t see 51 Pegasi b; no one has. By using a complex mathematical method called radial velocity, they witnessed the planet’s gravitational effect on its star and deduced that it must be there.

    There has been an explosion of knowledge in the relatively short time since, in part because of Seager’s pioneering theoretical work in using light to study the composition of alien atmospheres. When starlight passes through a planet’s atmosphere, certain potentially life-betraying gases, like oxygen, will block particular wavelengths of light. It’s a way of seeing something by looking for what’s not there.

    Light or its absence is also the root of something called the transit technique, a newer, more efficient way than radial velocity of finding exoplanets by looking at their stars. It treats light almost like music, something that can be sensed more accurately than it can be seen. The Kepler space telescope, launched in 2009 and now trailing 75 million miles behind Earth, detects exoplanets when they orbit between their stars and the telescope’s mirrors, making tiny but measurable partial eclipses.

    NASA/Kepler Telescope
    NASA/Kepler Telescope

    Planet transit. NASA/Ames
    Planet transit. NASA/Ames

    A planet the size of Jupiter passing in front of its sun might result in a 1 percent dip in the amount of starlight Kepler receives, a drop that, in time, reveals itself to be as regular as rhythm, as an orbit. The transit technique has led to a bonanza of finds. In May, NASA announced the validation of 1,284 exoplanets, by far the largest single collection of new worlds yet. There are now 3,414 confirmed exoplanets and an additional 4,696 suspected ones, the count forever increasing.

    Before Kepler, the nature of the transit technique meant that most of those exoplanets were “Hot Jupiters,” giant balls of hydrogen and helium with short orbits, making them scalding, lifeless behemoths. But in April 2014, Kepler found its first Earth-size exoplanet in its star’s habitable zone: Kepler-186f. It’s about 10 percent larger than Earth and orbits on the outer reaches of where the temperature could allow life. No one knows the mass, composition or density of Kepler-186f, but its discovery remains a revelation. Kepler was searching, somewhat blindly, an impossibly small sliver of space, and it found a potentially habitable world more quickly than anyone might have guessed.

    In August, astronomers at the European Southern Observatory announced that they had detected a somewhat similar planet orbiting Proxima Centauri, the single star closest to us after the sun.

    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker
    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker

    They named it Proxima Centauri b. Studying the data, Seager supported the discovery and agreed that it might boast a life-sustaining — or at least non-life-threatening — surface temperature. There are now nearly 300 confirmed exoplanets or candidates orbiting within the habitable zones of their stars. Extrapolating the math, NASA scientists now believe that there are tens of billions of potentially life-sustaining planets in the Milky Way alone. The odds practically guarantee that a habitable planet is somewhere out there and that someone or something else is, too.

    In some ways, the search for life is now where the search for exoplanets was 20 years ago: Common sense suggests a presence that we can’t confirm. Seager understands that we won’t know they’re out there until we more truly lay eyes on their home and see something that reminds us of ours. Maybe it’s the color blue; maybe it’s clouds; maybe, however many generations from now, it’s the orange electrical grids of alien cities, the black rectangles of their lightless Central Parks. But how could we ever begin to look that far? “Everything brave has to start somewhere,” Seager says.

    The beginning of her next potential breakthrough hangs on the wall opposite the window in her office. It is a two-thirds scale model of a single petal of something called the starshade.

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    She has been a leading proponent of the starshade project, and outside her teaching, it is one of her principal professional concerns.

    Imagine that far-off aliens with our present technology were trying to find us. At best, they would see Jupiter. We would be lost in the sun’s glare. The same is true for our trying to see them. The starshade is a way to block the light from our theoretical twin’s sun, an idea floated in 1962 by Lyman Spitzer, who also laid the groundwork for space telescopes like Hubble. The starshade is a huge shield, about a hundred feet across. For practical reasons that have to do with the bending of light, but also lend it a certain cosmic beauty, the starshade is shaped exactly like a sunflower. By Seager’s hopeful reckoning, one day the starshade will be rocketed into space and unfurled, working in tandem with a new space telescope like the Wfirst, scheduled to launch in the mid-2020s.

    NASA/WFIRST
    NASA/WFIRST

    When the telescope is aimed at a particular planetary system, lasers will help align the starshade, floating more than 18,000 miles away, between the telescope and the distant star, closing the curtains on it. With the big light extinguished, the little lights, including a potential Earthlike planet and everything it might represent, will become clear. We will see them.

    The trouble is that sometimes the simplest ideas are the most complicated to execute. About once a decade since Spitzer’s proposal — he could work out the math but not the mechanics — someone else has taken up the cause, advancing the starshade slightly closer to reality before technological or political inertia set in. Three years ago, Seager joined a new, NASA-sponsored study to try to overcome the final practical hurdles; NASA then chose her from among her fellow committee members to lead the effort.

    After those decades of false starts, Seager and her team have already succeeded in making the starshade seem like a real possibility. NASA recognized it as a “technology project,” which is astral-bureaucracy speak for “this might actually happen.” Today the starshade is a piece of buildable, functional hardware. Seager packs that single petal into a battered black case and wheels it, along with a miniature model of the starshade, into classrooms and conferences and the halls of Congress, trying to find the momentum and hundreds of millions of dollars that allow impossible things to exist.

    “If I want the starshade to succeed, I have to help mastermind it,” Seager says. “The world sees me as the one who will find another Earth.” She has her intelligence, and her credentials, and her audience. She has her focus. But maybe more than anything else, Seager understands in ways few of us do that sometimes you need darkness to see.

    Seager grew up in Toronto, wired in a way all her own. “Ever since I was a child, there was just something about me that wasn’t quite like the others,” she says. “Kids know how to sort through who’s the same and who’s different.” After her parents divorced, her father, Dr. David Seager, achieved a certain fame by becoming one of the world’s leaders in hair transplants. The Seager Hair Transplant Center still operates and bears his name a decade after his death. David Seager was besotted with his bright daughter and wanted her to become a physician.

    Seager did her best to fit in. Sometimes she did; mostly she didn’t. Eventually, she gave up trying. She still talks breathlessly — “without enough modulation,” she has learned by listening to other people talk. She has never had the patience to invest in something like watching TV. “Things just move too slowly,” she says. “It feels like a drag.” She sleeps a lot, but that’s just a concession to her biology; she recognizes that she’s a more efficient machine when she’s rested. But if Seager’s apartness didn’t make her insecure, it also made her feel as though the expectations of others didn’t apply to her. “I loved the stars,” she says. When she was 16, she bought a telescope.

    Friendless for most of her childhood, Seager eventually forged her way to her own vision of the good life. She found and married a quiet man named Mike Wevrick, whom she met on a ski trip with her canoe club. He had seen something in her that nobody other than her father fully saw; he saw her as special as well as strange. Later, she graduated from Harvard, an early expert in exoplanets. (51 Pegasi b was discovered just when she was searching for a thesis topic. “I was born at the perfect time,” she says.) She and Wevrick had Max and Alex; Seager was hired by M.I.T., and she and Wevrick and the boys moved into a pretty yellow Victorian in Concord, Mass. She took the train to work. Wevrick, a freelance editor, managed just about everything that didn’t involve the search for intelligent life in the universe. Seager never shopped for groceries or cooked or pumped gas. All she had to do was find another Earth.

    Then, in the fall of 2009, Wevrick got a stomachache that drove him to bed. They figured it was the flu. Wevrick didn’t have the flu, but a rare cancer of the small intestine. They were told that the initial prospects were good, and he fought the cancer sufferer’s systematic fight. But while laws govern astrophysics, cancer is an anarchist. About a year after Wevrick’s diagnosis, he and Seager went cross-country skiing, and he couldn’t keep up. A few more terrible months passed, and he began writing out a methodical three-page list, practical advice for Seager after his death. It wasn’t a love letter; it was an instruction manual for life on Earth. By June 2011, he was 47 and in home hospice. Seager asked him how to get the roof rack that carried his canoes off the car. “It’s too complicated to explain,” Wevrick said. That July, he died.

    The first couple of months after Wevrick’s death were weird. Seager felt a surprising sense of relief from the uncertainties of sickness, a kind of liberation. She didn’t care about conventions like money, which she had never needed to manage, and she took the boys on some epic trips. There are pictures of them smiling together in the deserts of New Mexico, on mountaintops in Hawaii. Then one day, she went into Boston for a haircut, got turned around and accidentally walked into a lawyer’s office next to the salon. Seager ended up talking to a woman inside. That woman was also a widow, and she told Seager that there would be a moment, as inevitable as death itself, when her feelings of release would be replaced by the more lasting aimlessness of the lost. Seager walked back outside, and just like that, the world came out from under her feet. She fell into an impossible blackness.

    Later that winter, she took the boys sledding at the big hill in Concord. Two other women and their children were there. Seager stared at them coldly. They were smiling and carefree with their perfect, blissful lives. Seager felt ugly and ruined next to them. Then Alex, who was 6 at the time, had a meltdown. He sprawled himself across the hill so that the other children couldn’t go down it. The two other mothers tried to get him to move. “He has a problem,” Seager told them. They continued to try to shift him.

    “HE HAS A PROBLEM,” Seager said. “MY HUSBAND DIED.”

    “Mine, too,” one of the other women said. That was Melissa. A few weeks later, on Valentine’s Day, Seager was invited to her first gathering of the widows.

    Today, Melissa says she could detect the telltale “flintiness” of the recently bereaved the moment she saw Seager on the hill. Now there were six widows united in Concord, each middle-aged, each in a different stage of grief, drawn together by the peculiar pull of the unlucky. Three had been widowed by cancer, two by accidents — bicycling and hiking — and one by suicide. Melissa’s husband was four years gone, Seager’s seven months.

    Widowhood was like a new universe for Seager to explore. She had never understood many social norms. The celebration of birthdays, for instance. “I just don’t see the point,” she says. “Why would I want to celebrate my birthday? Why on earth would I even care?” She had also drawn a hard line against Christmas and its myths. “I never wanted my kids to believe in Santa.” After Wevrick’s death, she became even more of a satellite, developing a deeper intolerance for life’s ordinary concerns.

    Making dinner seemed an insurmountable chore, the routine of school lunches a form of torture. The roof needed to be replaced, and she didn’t have the faintest idea how to get it fixed. She wasn’t sure how to swipe credit cards. If the answers to her questions weren’t somewhere on Wevrick’s three wrinkled sheets of paper, it could feel as though they were locked in a safe.

    There was a pendant light in her front hall, where the boys would fight with their toy lightsabers, and sometimes they would hit the light with their wild swings. Seager decided that either the light or one of the boys was going to end up damaged. She asked the widows how to do electrical work — “I have to parcel out things with logic and evidence,” she says — got out the ladder and took down the light, carefully wrapping black tape around the ends of the bare wires that now poked through the hole in the ceiling. She remembers thinking that her removing that light, all by herself, represented the height of her new accomplishment. She felt so reduced. She felt so gigantic.

    For all of her real and perceived strangeness, the most unusual thing about Seager is her blindness to her greatest gift. She is more than aware of her preternatural mathematical abilities, her possession of a rare mind that can see numbers and their functions as clearly as the rest of us see colors and shapes. “I’m good at that stuff,” she says with her brand of factual certainty that is sometimes confused with arrogance. She knows she is unusually capable of turning abstract concepts into things that can be packed into a case. What she doesn’t always see is her knack for connection between places if not always people, the unconventional grace she possesses when it comes to closing unfathomable distances.

    Seager has lined the hallway outside her office with a series of magical travel posters put out by the Jet Propulsion Laboratory. Each gives a glimpse of the alien worlds that, in part because of her, we now know exist. There’s a poster for Kepler-16b, an exoplanet that orbits a pair of stars, like Luke Skywalker’s home planet of Tatooine. Kepler-186f is depicted with red grass and red leaves on its trees, because its star is cooler and redder than the sun, which might influence photosynthesis in foliage-altering ways. There’s even one for PSO J318.5-22, a rogue planet that doesn’t orbit a star but instead wanders across the galaxy, cast in perpetual darkness, swept by rain of molten iron.

    After the discovery of Proxima Centauri b, Seager wrote a galactic postcard from it for the website Quartz. She closed her eyes and imagined a world 25 trillion miles away. “For the average earthling,” she wrote, “visiting this planet might not be much fun.” She saw a planet perhaps a third larger than Earth, with an orbit of only 11 days. Given its proximity to its small, red star, she suggested that the ultraviolet radiation on Proxima Centauri b is probably intense but the light Martian-dim. She also deduced that Proxima Centauri b is “tidally locked.” Like the moon’s relationship to Earth, one side of the planet always faces its star, which is always in the same place in its sky. Parts of Proxima Centauri b are cast in perpetual sunrise or sunset. One side is always in darkness.

    At first, after Wevrick’s death, Seager thought about abandoning her work, because she was having such a hard time with her responsibilities at home. Her dean talked her out of quitting, giving her financial support to hire caregivers for the boys and urging her to redouble her efforts. “I had worked so hard,” she says. “I had all the years I called the lost years with Mike when I ignored him. We had little tiny kids. I was working all the time, exhausted all the time. But I was like: We’ll have money some day. We’ll have time some day.”

    She paused. Her face was blank, emotionless. “Now I’ll cry.” Seconds later, tears spilled out of her eyes, and her voice modulated. “I wanted to make it up to him, and I never did.”

    Seager has always found comfort and perhaps even solace in her work, in her search for another and maybe better version of our world. In her mourning, each discovery represented one more avenue of escape. In the spring of 2013, she was given responsibility for the starshade. That July, she met a tall, fast-walking man named Charles Darrow.

    Darrow, who is now 53, was an amateur astronomer and the president of the Toronto branch of the Royal Astronomical Society of Canada, and at the last minute he decided to go to the society’s annual meeting in Thunder Bay, Ontario. Darrow was on his way out of a profoundly unhappy marriage; he worked for his family business, an engine-parts wholesaler. He needed a break, and he pointed his car north. “I wanted to be alone,” he says. At a reception on the Friday evening, Darrow noticed a hazel-eyed woman staring at him from across the room. “I thought she was looking at someone behind me,” he says. Then he went into the lecture hall, and the same woman was that night’s keynote speaker. She talked about exoplanets. The next day, lunch was in a university cafeteria. The woman was in the salad line ahead of him, and she turned around. Darrow mustered up his courage and invited Sara Seager to join him. “I knew about five minutes into the conversation that my life was going to change,” he says.

    Seager was taken with Darrow the night she saw him in Thunder Bay. She had been struck by the contrast between the whiteness of his shirt and his tanned summer skin. But she didn’t have the same certainty that possessed him at their lunch the next day. She wasn’t sure how to develop a relationship across the 549 miles between her home in Concord and his home outside Toronto. She thought they might never cross paths again.

    They might not have, except Darrow resolved during his drive back home that he had to call her. He picked up the phone five times but always hung up before she answered. On the sixth, he spoke to her, beginning a long correspondence, emails and conversations over Skype. Darrow and Seager talked every way but face to face. They fell in love remotely. “I had to follow my heart,” Darrow says. “I decided that I wasn’t going to die unhappy.”

    Melissa, meanwhile, told Seager that if she could close the gap between here and a planet like Kepler-186f — a journey that would take us 500 light-years to complete — then the 549 miles between Concord and Toronto shouldn’t seem like such an insurmountable gulf. By her usual measures, he was right next door.

    Seager and Darrow married in April 2015. In different ways, each had rescued the other. Seager was the cataclysm that allowed Darrow to make every correction. He divorced, left his family business and moved into a pretty yellow Victorian in Concord. The two boys started calling him dad. For Seager, Darrow was a second chance to know love, even deeper than the one she had known, because it seemed so improbable in her sadness. “I feel so lucky to have found him,” Seager says. “What are the chances?”

    Adapting to his new life hasn’t always been easy for Darrow. He is determined, as he puts it, “to make Sara the happiest woman in the multiverse.” He cooks dinner; he helps take care of the boys; he maintains the house; he walks with Seager to the train station every morning, and he picks her up every night. He has chosen to take care of the mundane so that she can devote herself to the extraordinary. But he banged his head more than once on Wevrick’s canoe, which still hung from the back of the garage.

    Not long ago, Darrow was looking for the right ways to assert his presence, to make a claim to a house that didn’t always feel like his. The wires dangling from the front hall ceiling bothered him. They looked bad and seemed dangerous. A few months after his arrival in Concord, he took his opening. He carved out some of the plaster, installed a plastic box, ran the wires through it and hooked up a new fixture, flush mounted, so that the boys wouldn’t hit it during their duels.

    Darrow climbed down from the ladder and flicked the switch.

    The morning after she forgot her phone, Seager woke up and decided, just like that, to skip the commute. With the house to herself, she tried to make coffee. She left out part of the machine, and after some terrible noises, the pot was bone dry. She sat down at her kitchen table with her empty mug and began talking about hundreds of billions of galaxies and their hundreds of billions of stars. Tens of billions of habitable planets, far more of them than there are people on Earth. There has to be other life somewhere out there. We can’t be that special.

    “It would be arrogant to think so,” Seager said. But in her lifetime, after the Wfirst telescope rockets into orbit, and maybe her starshade follows it — she puts the chances of success at 85 percent — she will have time to explore only the nearest hundred stars or so. A hundred stars out of all those lights in the sky, a fraction of a fraction of a fraction.

    Will one of them have a small, rocky planet like Earth? Probably. Will one of those small, rocky planets have liquid water on it? Possibly. Will the planet sustain life? Now the odds tilt. Now they are working against her, and she knows it. Now they’re maybe one in a million that she’ll find what she’s looking for.

    She did some private math. “I believe,” she said.

    Seager’s discovery will be fate-altering if it comes, but it will also be quiet, a few pixels on a screen. It will obey the laws of physics. It will be a probability equation: What are the chances? We won’t discover that there is life on other planets the way we’ve been taught that we’ll learn. There won’t be some great mother ship descending from the sky over Johannesburg or a bizarre lightning storm that monsters will ride to New Jersey. What Seager will have is a photograph from a space telescope of a distant solar system, with its star eclipsed by her starshade, and with a familiar blue dot some safe and survivable distance away from it. That’s all the evidence she will have that we’re not alone, and that will be all the evidence she will need. Her proof of life will be a small light where there wasn’t one before.

    See the full article here .

    Please help promote STEM in your local schools.

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  • richardmitnick 1:37 pm on September 28, 2016 Permalink | Reply
    Tags: , Astrophysics, , , , How Do We Classify The Stars In The Universe?   

    From Ethan Siegel: “How Do We Classify The Stars In The Universe?” 

    Ethan Siegel

    Sep 28, 2016

    1
    The stars found in NGC 3532 show a rich variety of colors and brightnesses. Image credit: ESO/G. Beccari.

    Take a look up at a dark night sky, and you’ll find it illuminated by hundreds or even thousands of individual twinkling points of light. While they might seem, to an untrained eye, to all be the same — except for, perhaps, some appearing brighter than others — a closer look reveals a number of intrinsic differences between them. Some of them appear redder or bluer than others; some are intrinsically brighter or fainter, even if they’re the same distance away; some have larger physical sizes than others; some have greater or lesser percentages of heavy elements in them. For a long time, scientists didn’t know how stars worked or what made one type different from another. Yet at the start of the 20th century, the pieces all came together to figure out exactly how the different stars should be classified, and we owe it all to a woman you might not have heard of: Annie Jump Cannon.

    2
    Annie Jump Cannon sitting at her desk at Harvard College Observatory, sometime in the early 20th century. Image credit: Smithsonian Institution from the United States.

    With either good enough skies and a trained observer, or with a quality telescope, a look at the stars immediately shows that they come in different colors. Because temperature and color are so closely related — heat something up and it glows red, then orange, then yellow, white and eventually blue as you turn up the temperature — it makes sense that you’d classify them based on color. But where would you make those divisions, and would those divisions encapsulate all the important physics and astrophysics going on? Without more information, there wouldn’t be a good, universal system that everyone would agree on. But the study of color in astronomy (photometry) can be augmented by breaking up the light into individual wavelengths (spectroscopy). If there are either neutral or ionized atoms in the outermost layers of the star, they’ll absorb some of the light at particular wavelengths. These absorption features can add an extra layer of information, and led to the earliest useful classification system.

    3
    The solar spectrum shows a significant number of features, each corresponding to absorption properties of a unique element in the periodic table. Image credit: Nigel A. Sharp, NOAO/NSO/Kitt Peak FTS/AURA/NSF.

    NOAO Kitt Peak National Observatory  on the Tohono O’odham reservation outside Tucson, AZ, USA
    NOAO Kitt Peak National Observatory on the Tohono O’odham reservation outside Tucson, AZ, USA

    Known as Secchi classes, for the 19th century Italian astronomer Angelo Secchi who devised them, there were originally three types:

    1. Class I: a class for the blue/white stars that exhibited strong, broad hydrogen lines.
    2. Class II: yellow stars with weaker hydrogen features, but with evidence of rich, metallic lines.
    3. Class III: red stars with complex spectra, with huge sets of absorption features.

    This system, first laid out in 1866, was the first non-arbitrary system of classification, since it relied on a combination of spectroscopic features in tandem with the photometric colors. While Secchi went on to further refine his class structure and introduce sub-classes and additional classes, this became superseded by finer spectral delineations.

    5
    The original three Secchi classes, and the accompanying spectra that go along with them. Image credit: from a colored lithograph in a book published around 1870, retrieved from AIP.

    Researchers at Harvard College Observatory were tasked with surveying all the stars visible in the night sky down to a visual magnitude of +9, or the faintest you’d be able to see today with a very nice pair of binoculars. Except it wasn’t enough to record them in the traditional fashion; they needed to be observed and analyzed spectroscopically. Under the guidance of Edward Pickering, a group of astronomers — all women, known at the time as “Pickering’s Harem” (that was later sanitized to “Pickering’s Women” or the “Harvard Computers”) — took the data and created the Draper System, for which Pickering was given sole/full credit. The stars that had the strong hydrogen lines (Secchi Class I) were broken up into four further delineations, labeled A through D, based on how strong the hydrogen absorption features were, with A being the strongest. The stars with rich, metallic lines (and weaker hydrogen lines, Secchi Class II) were broken up into six classes, E through L, with decreasing hydrogen strength and increasing metal strength going hand-in-hand. The reddest stars, richest in absorption features (Secchi Class III) became class M. In addition, there were four other types labeled N through Q, with O being notable as having very bright, blue stars with very weak hydrogen features, but also lines not seen in any other star class.

    6
    The seven major star classes, organized by their colors. It turns out that these colors also correspond to a star’s surface temperature, and so O-stars are the hottest, while M-stars are the coolest. Image credit: E. Siegel.

    In 1901, Annie Jump Cannon — one of the astronomers working under Pickering — synthesized the full suite of this data and consolidated the seventeen Draper System classes into just seven: A, B, F, G, K, M, and O. The big step that she took, however, was also perhaps the simplest: to reorder them by their color, from bluest to reddest. This meant the order was now O, B, A, F, G, K, and M. Star types were further broken down into ten intervals apiece, from 0 to 9, based on bluest to reddest. So a B2 star would be 20% of the way between a B0 star and an A0 star, a B5 star would be 50% of the way there, and a B9 star would be 90% of the way there. The bluest star of all would be O0, while the reddest would be M9. This system, known as the Harvard Spectral Classification System, is still in use today. There would, however, be one more great leap that would happen decades after Annie Jump Cannon’s contributions, and you can see it for yourself if you view the spectra of these different classes in descending order.

    6
    O-stars, the hottest of all stars, actually have weaker absorption lines in many cases, because the surface temperatures are great enough that most of the atoms at its surface are at too great of an energy to display the characteristic atomic transitions that result in absorption. Image credit: NOAO/AURA/NSF, modified to illustrate the stars that demonstrate this phenomenon.

    You’ll notice that certain lines appear, get stronger and then disappear, while others simply appear and strengthen. The reason stars appear with the absorption features they do are because of their temperature, and because at certain temperatures different ionization states (and hence, different atomic transitions) are more common, and therefore, stronger. The link between temperature, color and ionization wasn’t found until 1925, with the Ph.D. dissertation of Cecilia Payne, which also enabled us to determine what the Sun (and all stars) were actually made out of! The different stellar classifications don’t just correspond to a star’s colors and absorption features, but to a star’s temperature as well.

    8
    The (modern) Morgan–Keenan spectral classification system, with the temperature range of each star class shown above it, in kelvin. Image credit: Wikimedia Commons user LucasVB, additions by E. Siegel.

    Thanks to Payne and Cannon’s work, we learned that stars were made out of mostly hydrogen and helium, and not out of heavier elements like Earth is. Cecilia Payne’s work would have been impossible without Annie Jump Cannon’s data; Cannon herself was responsible for classifying, by hand, more stars in a lifetime than anyone else: around 350,000. She could classify a single star, fully, in approximately 20 seconds, and used a magnifying glass for the majority of the (faint) stars. Her legacy is now nearly 100 years old: on May 9, 1922, the International Astronomical Union formally adopted Annie Jump Cannon’s stellar classification system. With only minor changes having been made in the 94 years since, it is still the primary system in use today.

    See the full article here .

    Please help promote STEM in your local schools.

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 4:04 pm on September 19, 2016 Permalink | Reply
    Tags: 2017 ESO Calendar, , Astrophysics, ,   

    ESO: The 2017 Calendar is now available at the ESOshop 

    ESO 50 Large

    European Southern Observatory

    The 2017 ESO Calendar is now available from the ESOshop.

    1
    Price € 9.99

    This is a stunning calendar. There are images from La Silla, ALMA and Paranal and many images from ESO’s amazing astronomical projects.

    You might even buy some for gifts to your friends in Astronomy.

    Please help promote STEM in your local schools.
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    Visit ESO in Social Media-

    Facebook

    Twitter

    YouTube

    ESO Bloc Icon

    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    LaSilla

    ESO VLT
    VLT

    ESO Vista Telescope
    VISTA

    ESO NTT
    NTT

    ESO VLT Survey telescope
    VLT Survey Telescope

    ALMA Array
    ALMA

    ESO E-ELT
    E-ELT

    ESO APEX
    Atacama Pathfinder Experiment (APEX) Telescope

     
  • richardmitnick 7:36 am on September 16, 2016 Permalink | Reply
    Tags: , Astrophysics, , , How Certain Are We Of The Universe's 'Big Freeze' Fate?   

    From Ethan Siegel: “How Certain Are We Of The Universe’s ‘Big Freeze’ Fate?” 

    From Ethan Siegel

    Sep 15, 2016

    1
    The four possible fates of the Universe with only matter, radiation, curvature and a cosmological constant allowed. Image credit: E. Siegel, from his book, Beyond The Galaxy.

    Ever since the expanding Universe was first discovered by Hubble himself, one of the greatest existential questions of all — what will the fate of the Universe be? — suddenly leaped from the realm of poets, philosophers and theologians into the realm of science. Rather than an unknown mystery for human mental gymnastics, it became a question that the acquisition of data and a knowledge of what existed and was observable could answer. The discovery that the Universe was full of galaxies, that it was expanding and that the expansion rate could be measured, both today and in the past, meant that we could use our best scientific theories to accurately predict how the Universe would behave in the future. And for decades, we weren’t sure what the answer would be.

    2
    The star in the great Andromeda Nebula that changed our view of the Universe forever, as imaged first by Edwin Hubble in 1923 and then by the Hubble Space Telescope nearly 90 years later. Image credit: NASA, ESA and Z. Levay (STScI) (for the illustration); NASA, ESA and the Hubble Heritage Team (STScI/AURA) (for the image).

    A number of astronomers and physicists were detractors of cosmology (the study of the Universe), deriding it as a science, claiming that it was merely “a search for two parameters.” Those parameters were the Hubble constant, or the present rate of expansion, and the so-called deceleration parameter, which measured how the Hubble rate was changing over time. But if the physics of General Relativity was correct, those two things would be everything we needed to know to understand the Universe’s fate. The more distant you can observe an object, the farther back in time you look. And in an expanding Universe, when you see the Universe at a younger time, not only are galaxies closer together, but they’re moving apart from one another at a faster rate! In other words, the Hubble “constant” isn’t really a constant, but is decreasing over time.

    3
    In the distant past, the Universe expanded at a much greater rate, and is now expanding more slowly than it ever has before. The best map of the CMB and the best constraints on dark energy from it. Images credit: NASA / CXC / M. Weiss.

    But how it decreases over time is dependent on all the different types of energy present in the Universe. Radiation (like photons) behave differently from neutrinos, which behave differently from matter, which behaves differently from cosmic strings, domain walls, a cosmological constant or some other form of dark energy. Normal matter is simply conserved mass, so as the volume of space increases (as the scale of the Universe, a, cubed), the matter density drops as a-3. The wavelength of radiation stretches as well, so its density drops as a-4. Neutrinos first act like radiation (a-4) and then like matter (a-3) once the Universe cools past a certain point. And cosmic strings (a-2), domain walls (a-1) and a cosmological constant (a0) all evolve according to their own physical specifications.

    4
    How matter (top), radiation (middle), and a cosmological constant (bottom) all evolve with time in an expanding Universe. Image credit: E. Siegel, from his book, Beyond the Galaxy.

    If you know what the Universe is made up of at any given moment, however, and you know how fast it’s expanding at that moment, you can determine — thanks to physics — how the Universe will evolve in the future. And that extends, if you like, into the future arbitrarily far, limited only by the accuracy of your measurements. Given the best data from Planck (the CMB), from the Sloan Digital Sky Survey (for Baryon Acoustic Oscillations/Large-scale structure), and from type Ia supernovae (our most distant “distance indicator”), we’ve determined that our Universe is:

    68% dark energy, consistent with a cosmological constant,
    27% dark matter,
    4.9% normal matter,
    0.1% neutrinos,
    and 0.01% photons,

    for a total of 100% (within the measurement errors) and with an expansion rate today of 67 km/s/Mpc.

    5
    The best map of the CMB and the best constraints on dark energy from it. Images credit: ESA & the Planck Collaboration (top); P. A. R. Ade et al., 2014, A&A (bottom).

    If this is 100% accurate, with no further changes, it means that the Hubble rate will continue to drop, asymptoting somewhere around a value of ~45 km/s/Mpc, but never dropping below it. The reason it never drops to zero is because of dark energy: the energy inherent to space itself. As space expands, the matter and other entities within it may get more dilute, but the energy density of dark energy remains the same. This means that an object that’s 10 Mpc away in the future will recede at 450 km/s; millions of years later, when it’s 20 Mpc away, it recedes at 900 km/s; later on it will be 100 Mpc away and receding at 4,500 km/s; by time it’s 6,666 Mpc away it recedes at 300,000 km/s (or the speed of light), and it moves away faster and faster without fail. In the end, everything that’s not already gravitationally bound to us will expand beyond our reach. In fact, 97% of the galaxies in the Universe are already gone, as even at the speed of light we’d never reach them, even if we left today.

    6
    The observable (yellow) and reachable (magenta) portions of the Universe. Image credit: E. Siegel, based on work by Wikimedia Commons users Azcolvin 429 and Frédéric MICHEL.

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey
    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey”

    But dark energy may not be truly a constant. We might have measured that it evolves as a0 according to our best measurements, but realistically, the best we can say is that it evolves as a0±0.08, where there’s a little bit of wiggle room in the exponent. Moreover, it could change over time, where dark energy could become more positive, more negative, or could even reverse its sign. If we wanted to be honest about what dark energy can and cannot be, it’s more accurate to showcase that wiggle room as well.

    7
    The blue “shading” represent the possible uncertainties in how the dark energy density was/will be different in the past and future. The data points to a true cosmological “constant,” but other possibilities are still allowed. Image credit: Quantum Stories.

    In the end, all we can go off of is what we’ve measured, and admit that the possibilities of what’s uncertain could go in any number of directions. Dark energy appears consistent with a cosmological constant, and there’s no reason to doubt this simplest of models in describing it. But if dark energy gets stronger over time, or if that exponent turns out to be a positive number (even if it’s a small positive number), our Universe might end in a Big Rip instead, where the fabric of space gets torn apart. It’s possible that dark energy may change over time and reverse sign, leading to a Big Crunch instead. Or it’s possible that dark energy may increase in strength and undergo a phase transition, giving rise to a Big Bang once again, and restarting our “cyclical” Universe.

    8
    The different ways dark energy could evolve into the future. Remaining constant or increasing in strength (into a Big Rip) could potentially rejuvenate the Universe. Image credit: NASA/CXC/M.Weiss.

    The smart money is on the Big Freeze, since nothing about the data indicates otherwise. But when it comes to the Universe, remember the golden rule: anything that hasn’t been ruled out is physically possible. And we owe it to ourselves to keep our mind open to all possibilities.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 4:57 pm on September 13, 2016 Permalink | Reply
    Tags: , Astrophysics, , Cosmic distance ladder, , ,   

    From Ethan Siegel: “GAIA Satellite To Find Out If We’re Wrong About Dark Energy And The Expanding Universe” 

    From Ethan Siegel

    Sep 13, 2016

    ESA/Gaia satellite
    ESA/Gaia satellite

    How far away are the most distant objects in the Universe? How has the Universe expanded over the course of its history? And therefore, how big and how old is the Universe since the Big Bang? Through a number of ingenious developments, humanity has come up with two separate ways to answer these questions:

    To look at the minuscule fluctuations on all scales in the leftover glow from the Big Bang — the Cosmic Microwave Background — and to reconstruct the Universe’s composition and expansion history from that.
    To measure the distances to the stars, the nearby galaxies, and the more distant galaxies individually, and reconstruct the Universe’s expansion rate and history from this progressive “cosmic distance ladder.”

    1
    The Gaia Deployable Sunshield Assembly (DSA) during deployment testing in the S1B integration building at Europe’s spaceport in Kourou, French Guiana, two months before launch. Image credit: ESA-M. Pedoussaut.

    Interestingly enough, these two methods disagree by a significant amount, and the European Space Agency’s GAIA satellite, poised for its first data release tomorrow, September 14th, intends to resolve it one way or another.

    2
    Image credit: ESA and the Planck Collaboration, of the best-ever map of the fluctuations in the cosmic microwave background.

    The leftover glow from the Big Bang is only one data set, but it’s perhaps the most powerful data set we could have asked for nature to provide us with. It tells us the Universe expands with a Hubble constant of 67 km/s/Mpc, meaning that for every Megaparsec (about 3.26 million light years) a galaxy is apart from another, the expanding Universe pushes them apart at 67 km/s. The Cosmic Microwave Background also tells us how the Universe has expanded over its history, giving us a Universe that’s 68% dark energy, 32% dark-and-normal matter combined, and with an age of 13.81 billion years. Beginning with COBE and heavily refined later by BOOMERanG, WMAP and now Planck, this is perhaps the best data humanity has ever obtained for precision cosmology.

    NASA/WMAP
    NASA/WMAP

    ESA/Planck
    ESA/Planck

    3
    The construction of the cosmic distance ladder involves going from our Solar System to the stars to nearby galaxies to distant ones. Each “step” carries along its own uncertainties. Image credit: NASA,ESA, A. Feild (STScI), and A. Riess (STScI/JHU).

    But there’s another way to measure how the Universe has expanded over its history: by constructing a cosmic distance ladder. One cannot simply look at a distant galaxy and know how far away it is from us; it took hundreds of years of astronomy just to learn that the sky’s great spirals and ellipticals weren’t even contained within the Milky Way! It took a tremendous series of steps to figure out how to measure astronomical distances accurately:

    We needed to learn how to measure Solar System distances, which took the developments of Newton and Kepler, plus the invention of the telescope.
    We needed to learn how to measure the distances to the stars, which relied on a geometric technique known as parallax, as a function of Earth’s motion in its orbit.
    We needed to learn how to classify stars and use properties that we could measure from those parallax stars in other galaxies, thereby learning our first galactic distances.
    And finally, we needed to identify other galactic properties that were measurable, such as surface brightness fluctuations, rotation speeds or supernovae within them, to measure the distances to the farthest galaxies.

    This latter method is older, more straightforward and requires far fewer assumptions. But it also disagrees with the Cosmic Microwave Background method, and has for a long time. In particular, the expansion rate looks to be about 10% faster: 74 km/s/Mpc instead of 67, meaning — if the distance ladder method is right — that the Universe is either younger and smaller than we thought, or that the amount of dark energy is different from what the other method indicates. There’s a big uncertainty there, however, and the largest component comes in the parallax measurement of the stars nearest to Earth.

    5
    The parallax method, employed by GAIA, involves noting the apparent change in position of a nearby star relative to the more distant, background ones. Image credit: ESA/ATG medialab.

    This is where the GAIA satellite comes into play. Outstripping all previous efforts, GAIA will measure the brightnesses and positions of over one billion stars in the Milky Way, the largest survey ever undertaken of our own galaxy. It expects to do parallax measurements for millions of these to an accuracy of 20 micro-arc-seconds (µas), and for hundreds of millions more to an accuracy of 200 µas. All of the stars visible with the naked eye will do even better, with as little as 7 µas precision for everything visible to a human through a pair of binoculars.

    6
    A map of star density in the Milky Way and surrounding sky, clearly showing the Milky Way, large and small Magellanic Clouds, and if you look more closely, NGC 104 to the left of the SMC, NGC 6205 slightly above and to the left of the galactic core, and NGC 7078 slightly below. Image credit: ESA/GAIA.

    GAIA was launched in 2013 and has been operational for nearly two full years at this point, meaning it’s collected data on all of these stars at many different points in our planet’s orbit around the Sun. Obtaining parallax measurements means we can get the full three-dimensional positions of these stars in space, and can even infer their proper motions at these accuracies, meaning we can dramatically reduce the uncertainties in the distances to the stars. What’s most spectacular is that many of these stars will be of the same types that we can measure in other star clusters and galaxies, enabling us to build a better, more robust cosmic distance ladder. When the GAIA results come out — and have been fully analyzed by the astronomical community — we’ll have our best-ever understanding of the Universe’s expansion history and of the distances to the farthest galaxies in the Universe, all because we measured what’s happening right here at home.

    Inflationary Universe. NASA/WMAP
    Inflationary Universe. NASA/WMAP

    Right now, the Cosmic Microwave Background and the cosmic distance ladder are giving us two different answers to the question of the age, expansion rate and composition of our Universe. They’re not very different, but the fact that they disagree points to one of two possible things. Either one (or both) of the measurements are in error, or there’s a fundamental tension between these two types of measurement that might mean our Universe is a funnier place than we’ve realized to date. When the results from GAIA come out tomorrow, the great hope of most astronomers is that the previous parallax measurements will be shown to have been in error, and our best understanding of the Universe will hold up and be vindicated. But nature has surprised us before, and — if you’re hoping for something new — keep in mind that it just might do so again.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 11:45 am on September 13, 2016 Permalink | Reply
    Tags: , Astrophysics, , , Impossibly bright monster pulsars   

    From EarthSky: “Impossibly bright monster pulsars” 

    1

    EarthSky

    September 12, 2016
    Deborah Byrd

    Astronomers in Japan used a supercomputer and a hypothetical neutron star to explain blinking, enigmatic objects known as Ultra Luminous X-ray pulsars.

    1
    Supercomputer simulation results suggest a new lighthouse model for ULXs (Ultra Luminous X-ray sources). Red indicates stronger radiation. Arrows show the directions of photon flow. Image via NAOJ.

    Pulsars are objects in space that blink at very precise intervals. The widely accepted model to explain them is the lighthouse model, involving a rotating, very dense neutron star that emits a highly focused beam of radiation. We can only see the beam when it points toward Earth, much as we see the flash of a lighthouse beam when it’s pointed our way. There are many kinds of pulsars, with many peculiar physical manifestations, and, on September 8, 2016, a research group led by Tomohisa Kawashima at the National Astronomical Observatory of Japan announced their use of a supercomputer to add one more possibility to the list. These scientists said that the central energy source of enigmatic pulsating Ultra Luminous X-ray sources – called ULXs – could be neutron stars, not black holes as previously thought.

    Their paper is published in Publications of the Astronomical Society of Japan.

    Astronomers first noticed ULXs in the 1980s. In the intervening years, astronomers have found about one ULX per galaxy in some galaxies, but other galaxies contain many and some (like our Milky Way, so far) none at all. If you assume ULXs radiate equally in all directions, they are more consistently luminous than any known stellar process, but no one actually does assume that. Instead, the popular model to explain them has been the black hole model. It’s the classic model involving an object with strong gravity (the black hole) pulling gas from a companion star. As the gas falls towards the black hole, it collides with other gas, heating up and creating a luminous gas that astronomers actually observe when they see a ULX.

    Then, in 2014, the X-ray space telescope NuSTAR threw a wrench into the wide acceptance of the black hole model when it detected unexpected periodic pulsed emissions in a ULX named M82 X-2.

    NASA/NuSTAR
    NASA/NuSTAR

    The discovery of this ULX-pulsar has had astrophysicists scratching their heads because black holes shouldn’t be able to produce pulsed emissions.

    Kawashima’s team doesn’t use black holes in its model at all. Instead, the team’s computer simulations show that a neutron star can provide the necessary pulsed luminosity under certain conditions. The explanation involves some thorny physics, which you can read in their statement, but they also provided the two videos below to help explain.

    The first video shows an artist’s impression of the standard model of a pulsar. Photon beams are emitted from the magnetic poles of a neutron star. These photon beams twirl because of the misalignment between the magnetic poles and the rotation axis. As a result, the beams face towards an observer at regular intervals and pulsed emissions are observed coming from the neutron star.

    The second video shows the model suggested by Kawashima and colleagues’ simulations, which they called a new cosmic lighthouse model for ULXs. They said:

    “When gases (red) fall onto a neutron star, the accretion columns are heated by shock waves and shine brightly. Photons can escape from the columns through the sidewall and do not prevent additional gas from accreting. Therefore these columns continue to emit an enormous amount of photos. In this model, due to the misalignment between the accretion columns and the rotation axis, the appearance of the accretion columns changes periodically with the rotation of the neutron star. Dazzling pulsed emissions can be observed when the apparent area of the columns reaches maximum.”

    For more of the physics of this model, be sure to read the scientists’ statement at the Center for Computational Astrophysics (CfCA).

    This team said it is now planning to develop its work further by using this new lighthouse model to study the detailed observational features of the ULX-pulsar M82 X-2, and to explore other ULX-pulsar candidates.

    Bottom line: Astronomers in Japan used a supercomputer to provide an alternative model – involving a neutron star, not a black hole – to explain enigmatic pulsating Ultra Luminous X-ray sources (ULXs).

    See the full article here .

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  • richardmitnick 8:47 pm on September 12, 2016 Permalink | Reply
    Tags: , Astrophysics, , ,   

    From New Scientist: “First glimpse of a black hole being born from a star’s remains” 

    NewScientist

    New Scientist

    12 September 2016
    Anna Nowogrodzki

    1
    Born phoenix-like from the ashes of a dying star? Science Photo Library/Getty

    We’ve received a birth announcement from 20 million light years away, in the form of our first ever glimpse of what seems to be the birth of a black hole.

    When massive stars run out of fuel, they die in a huge explosion, shooting out high-speed jets of matter and radiation. What’s left behind collapses into a black hole, which is so dense and has such strong gravity that not even light can escape it.

    Or so the theory goes, anyway. Now, a team led by Christopher Kochanek at Ohio State University in Columbus have glimpsed something very special in data from the Hubble Space Telescope, from when it was watching the red supergiant star N6946-BH1, which is about 20 million light years from Earth.

    Fading star

    This star, first observed in 2004, was once about 25 times the mass of our sun. Kochanek and his colleagues found that for some months in 2009, the star briefly flared a million times brighter than our sun, then steadily faded away. New Hubble images show that it has disappeared in visible wavelengths, but a fainter source in the same spot is detectable in the infrared, as a warm afterglow.

    These observations mesh with what theory predicts should happen when a star that size crumples into a black hole. First, the star spews out so many neutrinos that it loses mass. With less mass, the star lacks enough gravity to hold on to a cloud of hydrogen ions loosely bound around it. As this cloud of ions floats away, it cools off, allowing the detached electrons to reattach to the hydrogen. This causes a year-long bright flare – when it fades, only the black hole remains.

    There are two other potential explanations for the star’s disappearing act: it could have merged with another star, or be hidden by dust. But they don’t fit the data: a merger would shine more brightly than the original star for much longer than a few months, and dust wouldn’t hide it for so long.

    “It’s an exciting result and long anticipated,” says Stan Woosley at Lick Observatory in California.

    “This may be the first direct clue to how the collapse of a star can lead to the formation of a black hole,” says Avi Loeb at Harvard University.

    A dark life cycle

    The find needs further confirmation, but that may not be far off. Material falling into the black hole would emit X-rays in a particular spectrum, which could be spotted by the Chandra X-ray Observatory. Kochanek says his group will be getting new data from Chandra in the next two months or so.

    If Chandra sees nothing, that doesn’t mean it’s not a black hole. In any case, the team will continue to look with Hubble – the longer the star is not there, the more likely that it’s a black hole. “Patience proves it no matter what,” says Kochanek.

    This data will help describe the beginning of the life cycle of a black hole, and will inform simulations of how black holes form and what makes a massive star form a neutron star rather than a black hole.

    Despite calling himself a “nasty pessimist”, Kochanek thinks it’s quite likely this is indeed the formation of a black hole. “I’m not quite at ‘I’d bet my life on it’ yet,” he says, “but I’m willing to go for your life.”

    See the full article here .

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  • richardmitnick 1:53 pm on September 9, 2016 Permalink | Reply
    Tags: , Astrophysics, , Confirming The Big Bang's Last Great Prediction, Cosmic Neutrinos Detected, , ,   

    From Ethan Siegel: “Cosmic Neutrinos Detected, Confirming The Big Bang’s Last Great Prediction” 

    From Ethan Siegel

    Sep 9, 2016

    1
    The Big Bang timeline of the Universe. Cosmic neutrinos affect the CMB at the time it was emitted, and physics takes care of the rest of their evolution until today. Image credit: NASA / JPL-Caltech / A. Kashlinsky (GSFC).

    The Big Bang, when it was first proposed, seemed like an outlandish story out of a child’s imagination. Sure, the expansion of the Universe, observed by Edwin Hubble, meant that the more distant a galaxy was, the faster it receded from us. As we headed into the future, the great distances between objects would continue to increase. It’s no great extrapolation, then, to imagine that going back in time would lead to a Universe that was not only denser, but thanks to the physics of radiation in an expanding Universe, hotter, too. The discovery of the cosmic microwave background [CMB] and the cosmic light-element background, both predicted by the Big Bang, led to its confirmation.

    CMB per ESA/Planck
    CMB per ESA/Planck

    But last year, a leftover glow unlike any other — of neutrinos — was finally seen. The final, elusive prediction of the Big Bang has finally been confirmed. Here’s how it all unfolded.

    2
    An illustration of the concept of Baryonic Acoustic Oscillations, which detail how large scale structure forms from the time of the CMB onward. This is also impacted by relic neutrinos. Image credit: Chris Blake & Sam Moorfield.

    Seventy years ago, we had taken fascinating steps forward in our conception of the Universe. Rather than living in a Universe governed by absolute space and absolute time, we lived in one where space and time were relative, depending on the observer. We no longer lived in a Newtonian Universe, but rather one governed by general relativity, where matter and energy cause the fabric of spacetime itself to curve. And thanks to the observations of Hubble and others, we learned that our Universe was not static, but rather was expanding over time, with galaxies getting farther and farther apart as time went on. In 1945, George Gamow made perhaps the greatest leap of all: the great leap backwards. If the Universe were expanding today, with all the unbound objects receding from one another, then perhaps that meant that all those objects were closer together in the past. Perhaps the Universe we live in today evolved from a denser state long ago. Perhaps gravitation has clumped and clustered the Universe together over time, while it was more even and uniform in the distant past. And perhaps  — since the energy of radiation is tied to its wavelength – that radiation was more energetic in the past, and hence the Universe was hotter long ago.

    3
    How matter and radiation dilute in an expanding Universe; note the radiation’s redshift to lower and lower energies over time. Image credit: E. Siegel.

    And if this were the case, it brought up an incredibly interesting set of events as we looked farther and farther back into the past:

    There was a time before large galaxies formed, where only small proto-galaxies and star clusters had come to be.
    Before that, there was a time before gravitational collapse had formed any stars, and all was dark: just primeval atoms and low-energy radiation.
    Prior to that, the radiation was so energetic that it could knock electrons off of the atoms themselves, creating a high-energy, ionized plasma.
    Even earlier than that, the radiation reached such levels that even atomic nuclei would be blasted apart, creating free protons and neutrons, and forbidding the existence of heavy elements.
    And finally, at even earlier times, the radiation would have so much energy that — through Einstein’s E = mc^2  —  matter-and-antimatter pairs would spontaneously be created.

    This picture is part of what’s known as the hot Big Bang, and it makes a whole slew of predictions.

    4
    An illustration of the cosmic history/evolution of the Universe since the inception of the Big Bang. Illustration: NASA/CXC/M.Weiss.

    Each one of these predictions, like a uniformly expanding Universe whose expansion rate was faster in the past, a solid prediction for the relative abundances of the light elements hydrogen, helium-4, deuterium, helium-3 and lithium, and most famously, the structure and properties of galaxy clusters and filaments on the largest scales, and the existence of the leftover glow from the Big Bang — the cosmic microwave background — has been borne out over time. It was the discovery of this leftover glow in the mid-1960s, in fact, that led to the overwhelming acceptance of the Big Bang, and caused all other alternatives to be discarded as non-viable.

    5
    Image credit: LIFE magazine, of Arno Penzias and Bob Wilson with the Holmdel Horn Antenna, which detected the CMB for the first time.

    But there was another prediction we haven’t talked about much, because it was thought to be untestable. You see, photons — or quanta of light — aren’t the only form of radiation in this Universe. Back when all the particles are flying around at tremendous energies, colliding into one another, creating and annihilating willy-nilly, another type of particle (and antiparticle) also gets created in great abundance: the neutrino. Hypothesized in 1930 to account for missing energies in some radioactive decays, neutrinos (and antineutrinos) were first detected in the 1950s around nuclear reactors, and later from the Sun, from supernovae and from other cosmic sources. But neutrinos are notoriously hard to detect, and they’re increasingly hard to detect the lower their energies are.

    6
    The energy/flux spectrum of the Big Bang’s leftover glow: the cosmic microwave background. Image credit: COBE / FIRAS, George Smoot’s group at LBL.

    That’s a problem, and it’s a big problem for cosmic neutrinos in particular. You see, by time we come to the present day, the cosmic microwave background (CMB) is only at 2.725 K, less than three degrees above absolute zero. Even though this was tremendously energetic in the past, the Universe has stretched and expanded by so much over its 13.8 billion year history that this is all we have left today. For neutrinos, the problem is even worse: because they stop interacting with all the other particles in the Universe when it’s only about one second after the Big Bang, they have even less energy-per-particle than the photons do, as electron/positron pairs are still around at that time. As a result, the Big Bang makes a very explicit prediction:

    There should be a cosmic neutrino background (CNB) that is exactly (4/11)^(1/3) of the cosmic microwave background (CMB) temperature.

    That comes out to ~1.95 K for the CNB, or energies-per-particle in the ~100–200 micro-eV range. This is a tall order for our detectors, because the lowest-energy neutrino we’ve ever seen is in the mega-eV range.

    7
    Image credit: IceCube collaboration / NSF / University of Wisconsin, via https://icecube.wisc.edu/masterclass/neutrinos. Note the huge difference between the CNB energies and all other neutrinos.

    So for a long time, it was assumed that the CNB would simply be an untestable prediction of the Big Bang: too bad for all of us. Yet with our incredible, precise observations of the fluctuations in the background of photons (the CMB), there was a chance. Thanks to the Planck satellite, we’ve measured the imperfections in the leftover glow from the Big Bang.

    Initially, these fluctuations were the same strength on all scales, but thanks to the interplay of normal matter, dark matter and the photons, there are “peaks” and “troughs” in these fluctuations. The positions and levels of these peaks and troughs tells us important information about the matter content, radiation content, dark matter density and spatial curvature of the Universe, including the dark energy density.

    8
    The best fit of our cosmological model (red curve) to the data (blue dots) from the CMB. Image credit: Planck Collaboration: P. A. R. Ade et al., 2013, A&A, for the Planck collaboration.

    There’s also a very, very subtle effect: neutrinos, which only make up a few percent of the energy density at these early times, can subtly shift the phases of these peaks and troughs. This phase shift – if detectable — would provide not only strong evidence of the existence of the cosmic neutrino background, but would allow us to measure its temperature at the time the CMB was emitted, putting the Big Bang to the test in a brand new way.

    9
    The fit of the number of neutrino species required to match the CMB fluctuation data. Image credit: Brent Follin, Lloyd Knox, Marius Millea, and Zhen PanPhys. Rev. Lett. 115, 091301 — Published 26 August 2015.

    Last year, a paper [Physical Review Letters] by Brent Follin, Lloyd Knox, Marius Millea and Zhen Pan came out, detecting this phase shift for the first time. From the publicly-available Planck (2013) data, they were able to not only definitively detect it, they were able to use that data to confirm that there are three types of neutrinos — the electron, muon and tau species — in the Universe: no more, no less.

    10
    The number of neutrino species as inferred by the CMB fluctuation data. Image credit: Brent Follin, Lloyd Knox, Marius Millea, and Zhen PanPhys. Rev. Lett. 115, 091301 — Published 26 August 2015.

    What’s incredible about this is that there is a phase shift seen, and that when the Planck polarization spectra came out and become publicly available, they not only constrained the phase shift even further, but — as announced by Planck scientists in the aftermath of this year’s AAS meeting — they finally allowed us to determine what the temperature is of this Cosmic Neutrino Background today! (Or what it would be, if neutrinos were massless.) The result? 1.96 K, with an uncertainty of less than ±0.02 K. This neutrino background is definitely there; the fluctuation data tells us this must be so. It definitely has the effects we know it must have; this phase shift is a brand new find, detected for the very first time in 2015. Combined with everything else we know, we have enough to state that yes, there are three relic neutrino species left over from the Big Bang, with the kinetic energy that’s exactly in line with what the Big Bang predicts.

    Two degrees above absolute zero was never so hot.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 2:07 pm on August 6, 2016 Permalink | Reply
    Tags: , Astrophysics, , , Where did the Big Bang happen?   

    From Ethan Siegel: “Where did the Big Bang happen?” 

    From Ethan Siegel

    8.6.16

    1
    This image represents the evolution of the Universe, starting with the Big Bang. The red arrow marks the flow of time. Image credit: NASA / GSFC.

    If you’re looking for a point in space, the answer is going to shock you.

    “The world you see, nature’s greatest and most glorious creation, and the human mind which gazes and wonders at it, and is the most splendid part of it, these are our own everlasting possessions and will remain with us as long as we ourselves remain.” -Seneca

    Of all the concepts and topics that get tossed around, the Big Bang is one of the most controversial. Sure, it’s a scientific theory that’s quite old — it’s been around since the 1940s — and the evidence in favor of it has been overwhelming since the 1960s. The idea is simple: that the Universe had a beginning. That it had a birthday. That there was a day without a “yesterday,” where matter, radiation and the expanding, cooling Universe we recognize did not exist before a certain moment in time. And yet, here we are. Which brings up a slew of questions to any curious mind. Mark Trubnikov is one such curious individual, and he wants to know:

    [A]re there any theories or experiments that can find out and prove our position in space according to the Big Bang point? I think that, as far, as we have very limited observation opportunities form our planet, that would be not so easy to determine the curvature of the space here… [W]hy do we think that the Big Bang happened in a point in the 3D-space? And why do we think that the Universe is a sphere?

    These are all good questions, and they’re all common conceptions that people have of the Universe, for good reason. But are these assertions true?

    1
    The evolution of large-scale structure in the Universe, from an early, uniform state to the clustered Universe we know today. Image credit: Angulo et al. 2008, via Durham University at http://icc.dur.ac.uk/index.php?content=Research/Topics/O6.

    We commonly think of the Big Bang as a literal “bang,” or an explosion. It’s true that the Universe was similar to a tremendous, energetic, expanding fireball in the very earliest stages. It was:

    full of particles and antiparticles of all different types, as well as radiation,
    all of which was expanding away from every other particle, antiparticle and quantum of radiation,
    all of which was cooling down and slowing down as it expanded.

    But I’ve carefully been using the word “expansion” rather than explosion when it comes to this phenomenon. An explosion is something that occurs at one location in space and whose debris emanates from that point. A supernova is an explosion; a gamma ray burst is an explosion; a bomb detonating is an explosion; a grenade igniting is an explosion.

    4
    An artist’s impression of supernova 1993J, an exploding star in the galaxy M81. Image credit: NASA, ESA, and G. Bacon (STScI).

    But the Big Bang is not an explosion. When we talk about “the hot Big Bang,” we’re talking about the very first moment that the Universe could be described by this particle, antiparticle and radiation-filled state. Where the Universe begins expanding and cooling from this state according to the laws of General Relativity, and where we head down the path towards antimatter annihilating away, atomic nuclei and then neutral atoms forming, and finally forming stars, galaxies and the large-scale structure we see today. The key to the first question is understanding exactly what the Universe was doing at that moment: at the moment where we can first describe it in this hot Big Bang framework.

    5
    The quark-gluon plasma of the early Universe. Image credit: Brookhaven National Laboratory.

    As far as we can tell, there was no special point. There was no “origin” to the Universe starting out this way. What all the evidence points to is a counterintuitive but no less true conclusion: that the Big Bang occurred everywhere all at once. The evidence for this is overwhelming, and comes from the Universe itself. The Universe, if we look at the large-scale structure, of how galaxies cluster, of what the leftover glow from the Big Bang looks like, of what the average density is in regions more than a few hundred million light years in size, etc., we find two important observational facts about our Universe: it appears to have the same properties everywhere, and it looks the same in all directions. In physics terms, this means the Universe is homogeneous (the same at all locations) and isotropic (the same in all directions).

    6
    Our view of a small region of the Universe, where each pixel in the image represents a mapped galaxy. On the largest scales, the Universe is the same in all directions and at all measurable location. Image credit: SDSS III, data release 8, of the northern galactic cap.

    You don’t get a Universe with those properties from an explosion, period. The “faster moving stuff” ends up the farthest away, but it also ends up the most diffuse over time; greater distances would appear to have fewer galaxies per unit volume, but they don’t in our Universe. Wherever the explosion occurred would be a clearly identifiable point. Because of how our Universe works, that point would have to be just a few million light years offset from the Milky Way, located just outside of the local group; statistically, with more than 170 billion galaxies in the Universe, the odds are about 100 times worse than winning either the Powerball or the Mega Millions jackpot.

    The fact that the Universe is homogeneous and isotropic tells us that the Big Bang happened simultaneously, some 13.8 billion years ago, at all locations equally. But we can’t see it at all locations equally; we can only see it from where we are. Our vantage point is inherently limited. Which is why you often see illustrations like the one below: of our Universe as seen from where we are, and with us at the center.

    7
    Artist’s logarithmic scale conception of the observable universe. Image credit: Wikipedia user Pablo Carlos Budassi.

    But this does not mean that the Universe is a sphere! In fact, if we want to know the shape of the Universe, it’s something we can actually measure, and place constraints on. If you walk outside and send two of your buddies in different directions so that you can all see each other, the three of you will form a triangle. Each one of you can measure the angle the other two appear to be at, relative to your point of view. If you then know those three angles, you can add them up: you’d expect them to be 180º, because that’s how many degrees are in the three angles of any triangle.

    Any triangle, that is, that’s in flat space.

    8
    The angles of a triangle add up to different amounts depending on the spatial curvature present. Image credit: NASA / WMAP science team.

    As it turns out, space doesn’t need to be flat! It could be negatively curved, like the surface of a horse’s saddle, where the angles add up to less than 180º. Or it could be positively curved, like the surface of a sphere, where the angles add up to more than 180º. If you stood on the equator in South America, your friend stood on the equator in Africa and another friend stood at the North Pole, you’d discover that the difference was significant: you’d wind up with a number closer to 270º than 180º. Well, we don’t have friends who can tell us what angles they see in space, but we have something just as good: the fluctuations in the Cosmic Microwave Background, which would have very different appearances depending on what the curvature of space actually is.

    9
    The appearance of different angular sized of fluctuations in the CMB results in different spatial curvature scenarios. Image credit: the Smoot group at Lawrence Berkeley Labs, via http://aether.lbl.gov/universe_shape.html.

    Well, we’ve made those observations, and what we’ve found is overwhelming: the Universe is flat, as far as we can tell. Really, really flat. In fact, the latest joint data from Planck and from the Sloan Digital Sky Survey tell us that if the Universe is curved — either positively or negatively — it’s on a scale that’s at least 400 times larger than the part of our Universe observable to us. And that part, the part we can see, is over 92 billion light years across.

    10
    And that’s just the part we can see. As far as our theories indicate, there’s very likely much more Universe just like our own outside of what we can observe. Image credit: E. Siegel, based on work by Wikimedia Commons users Azcolvin 429 and Frédéric MICHEL.

    So the Big Bang happened everywhere at once, 13.8 billion years ago, and our Universe is spatially flat to the best we can measure it at present. The Big Bang did not happen at a point, and the way we can tell is through the extraordinarily high degree of isotropy and homogeneity of the Universe. (It’s so good that when we notice an inhomogeneity that’s 0.01% of the Universe’s average, we wonder if something’s wrong!) So if you want to assert that the Big Bang happened exactly where you are, and that you’re right at the center of where it all started, no one can tell you that you’re wrong. It’s just that everyone, everywhere, in the entire Universe is just as right as you are when they make that claim, too.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
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