Astronomers have determined beyond all reasonable doubt that the heart of the Milky Way is a supermassive black hole, two research teams say. Astronomers have inferred the existence of a gravitational monster in the center of our galaxy for years, but the new results are “the best empirical evidence that super-massive black holes do really exist” [CNN], said researcher Reinhard Genzel.
Similar supermassive black holes are thought to form the center of many spiral and elliptical galaxies, and astronomer Robert Massey says the results suggest that galaxies form around giant black holes in the way that a pearl forms around grit. Dr Massey said: “Although we think of black holes as somehow threatening, in the sense that if you get too close to one you are in trouble, they may have had a role in helping galaxies to form – not just our own, but all galaxies” [BBC News]. Massey explains that if a black holes brings enough matter together in a dense cluster, it creates ripe conditions for the formations of stars and galaxies.
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A massive burst of gamma rays from a star that exploded billions of years ago reached Earth on March 19, and clocked in as the brightest burst of gamma rays ever observed, astronomers say. The blast, dubbed GRB 080319B, came from 7.5 billion light years away, more than halfway across the universe. Despite the immense distance, it would have been visible with the naked eye at dark sites on Earth for 40 seconds [New Scientist]. Researchers say they burst was so bright because the jet of matter and energy was pointed directly at Earth.
Gamma ray bursts, the universe’s most luminous explosions, occur when massive stars, perhaps 20 to 30 times the mass of the sun, burn out their nuclear fuel. As a star’s core collapses, it creates a black hole that drives powerful gas jets outward [Reuters]. The collisions of particles within those jets create high-energy gamma rays, which heat up surrounding gas and produce visible light. Nobody knows whether anyone looked up at the right spot in the sky at the right moment on March 19 to see the pulse of light, but NASA’s robotic Swift observatory did what it’s supposed to when it detects a gamma-ray burst, and swung into action [Ars Technica].
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Researchers have gotten the closest look yet at the supermassive black hole that is believed to lurk in the center of the Milky Way, using radio telescopes to peer through the cosmic dust. Lead astronomer Sheperd Doeleman says: “One of the problems with looking at this particular source is that we have to look through our galaxy. It’s a blessing that it’s this close, but it’s a curse because it’s obscured by gas and dust” [SPACE.com].
Black holes can’t be directly observed, because their gravitational pull is so strong that nothing, not even visible light, can escape. To study our local gravitational monster, researchers homed in on Sagittarius A*, the bright radio-emitting body thought to mark the position of the black hole. Because Sagittarius A* is likely fueled by the black hole’s activity, a better look at the radio-emitting body can provide more details about the black hole [Science News].
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Yesterday, NASA released the first set of images from its newest space telescope, the Gamma-Ray Large Area Space Telescope, which has now been renamed Fermi in honor of the particle physicist Enrico Fermi. After less than three months of collecting data, the Fermi telescope produced a map of the sky showing the sources of powerful gamma rays as bright spots of light.
“I like to call it our extreme machine,” said Jon Morse, the director of astrophysics for NASA. “It will help us crack the mysteries of these enormously powerful emissions.” Gamma rays are powerful light rays invisible to the naked eye [Washington Post]. As the Earth’s atmosphere absorbs gamma rays, they can only be studied from an orbiting telescope.
The $700 million telescope will observe gamma rays emitted by black holes, neutron stars, and other cosmic eccentrics, and will also scan the skies for the mysterious gamma ray bursts that are of special interest to astronomers because they are among the brightest events ever observed. The intense flashes of gamma rays can release within seconds the same amount of energy that the sun will put out over its entire ten-billion-year lifetime—but no one is sure what causes them. The going theory is that the bursts are tied to the explosive deaths of massive stars, but exactly what types of stars and how the explosions are triggered remains a mystery [National Geographic News]. Already, the Fermi telescope has detected gamma ray bursts at a rate of about one a day.
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In the heart of the Perseus galaxy cluster lies a remarkable galaxy known as NGC 1275, which has long “filaments”of glowing gas that snake out from its center. Astronomers have tried to explain how these beautiful structures can have survived for so long, given that the filaments reach out from their home galaxy into the Perseus cluster, which is a hostile, high-energy environment with a strong, tidal pull of gravity.These combined forces should have ripped apart the filaments in a very short time, causing them to collapse into stars [The Independent].
Now, thanks to images from the Hubble Space Telescope, astronomers say they understand how the filaments have held their shape for over 100 million years: Magnetic fields are keeping the filaments together, they say. The magnetic fields … hold onto the filaments because they wield influence over charged particles – such as protons and electrons – in the filaments’ gas [New Scientist].
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For million of years after the Big Bang, the universe was a dark place filled only with wisps of hydrogen and helium, as well as the mysterious substance known as dark matter that makes up much of the universe’s mass. Now, researchers have finished running a sophisticated computer program that simulated those early cosmic conditions and replicated the production of the first primordial star, which cast the first rays of starlight out into the blackness. Researchers say that the new model shows that the first star was tiny, but rapidly grew to enormous proportions before either flaming out or collapsing.
In the early universe, researchers believe that clouds of dark matter gathered and compressed pockets of hydrogen and helium gases. According the researchers’ simulation, those areas reached a tipping point around 300 million years after the Big Bang, igniting the first nuclear reactions. Over the course of about 100,000 years, according to the model, the compressed gases reach densities roughly equivalent to that of liquid water on Earth. At that point, the gases inside the halo have formed a protostar, about one-hundredth the mass of the sun [Science News].
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Well, that’s a relief. After a long safety review, physicists have declared that the enormous atom smasher that’s expected to go online this fall won’t create tiny black holes that will “eat” our planet. So that’s one less thing to worry about.
The Large Hadron Collider, which is being built near Geneva, Switzerland, will do things with subatomic particles that humans have never done before, causing some people to worry that scientists might be unwittingly building a doomsday devise. The $8 billion machine is designed to accelerate protons, the building blocks of ordinary matter, to energies of 7 trillion electron volts and then bang them together to produce tiny primordial fireballs, miniature versions of the Big Bang. Physicists will comb the detritus from those fireballs in search of forces and particles and even new laws of nature that might have prevailed during the first trillionth of a second of time [The New York Times].
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There’s some weird stuff out there in the remote reaches of the universe, things that we humans have only caught occasional glimpses of, or things whose existence we’ve only guessed at. But astrophysicists hope they’ll be able to aim a telescope deep into those dark corners by sometime next week, if all goes well with the launch of the $690 million orbital telescope tomorrow.
The Gamma-Ray Large Area Space Telescope (GLAST), which has been cleared for launch, will scan the skies for gamma rays, the highest-energy form of radiation on the electromagnetic spectrum, and will then try to identify their origins. That’s when it will get really weird and wonderful.
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