Astronomers have uncovered yet another clue in their quest to understand the Universe’s early life: the most distant quasar ever observed. At a redshift of 7.1, it is a relic from when the cosmos was just 770 million years old – just 5% of its age today.
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Full story at Universe Today.
Showing posts with label black holes. Show all posts
Showing posts with label black holes. Show all posts
Friday, July 1, 2011
Wednesday, March 9, 2011
Cosmology 101: The Present
Welcome back! Last time, we discussed the first few controversial and eventful moments following the birth of our cosmos. Looking around us today, we know that in the span of just a few billion years, the universe was transformed from that blistering amalgam of tiny elementary particles into a vast and organized expanse just teeming with large-scale structure. How does something like that happen?
Read more...
Full story at Universe Today
Read more...
Full story at Universe Today
Wednesday, November 10, 2010
New picture of the night sky, thanks to Fermi.
Imagine a world shadowed each night by a giant cloud of mysterious, illuminated fog. From far outside our galaxy, one would observe the fog rising 25,000 light years above and below the plane of the Milky Way in two enormous plumes. In fact, this world is our own. Of course, you might be more inclined to believe me if you had the ability to see gamma rays.
The Milky Way, in visible light. Gamma rays are invisible to human eyes.
Image courtesy of erikaj121893.
The new discovery comes from a team of Harvard University scientists working with Fermi's Large Area Telescope (LAT). "This work presents a multiwavelength study of the inner Galaxy and identifies several large-scale gamma-ray features, most notably 2 large structures that we refer to as the 'Fermi bubbles'," wrote the team of astronomers in their recent paper. These Fermi bubbles could be millions of years old, but their origin is something of a mystery. Some have suggested that an ancient boom of star births may have later led to a clustered grouping of star deaths. A large number of supernovae occurring all at once could have injected enough energy into interstellar space to create the two plumes of gamma-ray emitting gas. Others, including Douglas Finkbeiner, a senior member of the team, believe that the massive black hole at the center of our galaxy gave rise to the bubbles. Many galaxies emit jets of high-energy radiation due to infalling material around a central black hole, and the Milky Way may be no exception.
The Fermi bubble structures. Image courtesy of Su et al..
It may seem odd that no one had detected these colossal structures before now. As it turns out, the Milky Way has a separate, amorphous halo of gamma-ray fog that prevented astronomers from observing the bubbles until recently. The bubbles, which are slightly more energetic than the ambient haze and have clearly-defined x-ray edges, were only apparent after subtracting this fog from LAT observations. Fermi continues to observe the universe at gamma-ray frequencies.
The Milky Way, in visible light. Gamma rays are invisible to human eyes.
Image courtesy of erikaj121893.
The new discovery comes from a team of Harvard University scientists working with Fermi's Large Area Telescope (LAT). "This work presents a multiwavelength study of the inner Galaxy and identifies several large-scale gamma-ray features, most notably 2 large structures that we refer to as the 'Fermi bubbles'," wrote the team of astronomers in their recent paper. These Fermi bubbles could be millions of years old, but their origin is something of a mystery. Some have suggested that an ancient boom of star births may have later led to a clustered grouping of star deaths. A large number of supernovae occurring all at once could have injected enough energy into interstellar space to create the two plumes of gamma-ray emitting gas. Others, including Douglas Finkbeiner, a senior member of the team, believe that the massive black hole at the center of our galaxy gave rise to the bubbles. Many galaxies emit jets of high-energy radiation due to infalling material around a central black hole, and the Milky Way may be no exception.
The Fermi bubble structures. Image courtesy of Su et al..
It may seem odd that no one had detected these colossal structures before now. As it turns out, the Milky Way has a separate, amorphous halo of gamma-ray fog that prevented astronomers from observing the bubbles until recently. The bubbles, which are slightly more energetic than the ambient haze and have clearly-defined x-ray edges, were only apparent after subtracting this fog from LAT observations. Fermi continues to observe the universe at gamma-ray frequencies.
Friday, September 3, 2010
Of strings and things.
Imagine a tiny thread of material, so infinitesimal that it is more than a quadrillion times smaller than a proton (no matter who you ask). Now imagine that same tiny thread being present at the heart of every single particle that makes up every atom that makes up every bit of matter we can observe in the universe. Got that? Good. Now imagine that the identity of every subatomic particle is determined by the precise vibration pattern of the tiny strand of material within; that is, its precise vibration pattern... in ten dimensions. Welcome to the world of superstring theory, one of the most potent contenders for the long sought-after "Theory of Everything" that will combine general relativity and quantum mechanics into one, all-inclusive framework.
As always, xkcd cuts right to the heart of things.
Simply put, string theory elegantly exploits the physical principles of music; that is, plucking a string will generate a different sound, depending on the properties of the string and how hard it is plucked. Some variations of string theory predict that strings are open, with two endpoints, while others predict that strings are closed, like a loop. Either way, it is the specific modes of vibration, or excitations, of the string that give rise to different kinds of particles.
String theorists conceive of elementary particles as having a very small dimension of length, rather than being point particles with no length, width or height. It may seem like a simple change, but this assumption neatly does away with the problems scientists have always faced when trying to formulate a quantum theory of gravity. There is only one problem: scientists have had no way to test the predictions of string theory. Because strings are thought to be so incredibly small, particle accelerators would have to operate at astronomically high energies to probe deeply enough into the subatomic realm. We simply don't have the technology.
Not even CERN has the power to probe the mysteries of string theory.
Image courtesy of Image Editor.
But a new discovery by a researcher at Imperial College London might be about to change things. According to Professor Mike Duff, the math scientists use to apply string theory to black holes is exactly the same as the math that is used to describe quantum entanglement between three particles. In a paper published in this week's Physical Review Letters, Duff and his team of colleagues detail an experiment involving four entangled particles and predict the result based on the mathematics of string theory. If researchers can manage to carry out this experiment, and if the results agree with the team's predictions, string theory will finally have the experimental backing scientists have been seeking for decades.
Currently, there seems to be no practical connection between quantum entanglement and the string physics of black holes. Even Duff acknowledges that they are "unexpected and unrelated" areas of physics. Perhaps researchers are about to discover more than they bargained for. Or perhaps all of this is simply an odd, yet serendipitous, coincidence.
As always, xkcd cuts right to the heart of things.
Simply put, string theory elegantly exploits the physical principles of music; that is, plucking a string will generate a different sound, depending on the properties of the string and how hard it is plucked. Some variations of string theory predict that strings are open, with two endpoints, while others predict that strings are closed, like a loop. Either way, it is the specific modes of vibration, or excitations, of the string that give rise to different kinds of particles.
String theorists conceive of elementary particles as having a very small dimension of length, rather than being point particles with no length, width or height. It may seem like a simple change, but this assumption neatly does away with the problems scientists have always faced when trying to formulate a quantum theory of gravity. There is only one problem: scientists have had no way to test the predictions of string theory. Because strings are thought to be so incredibly small, particle accelerators would have to operate at astronomically high energies to probe deeply enough into the subatomic realm. We simply don't have the technology.
Not even CERN has the power to probe the mysteries of string theory.
Image courtesy of Image Editor.
But a new discovery by a researcher at Imperial College London might be about to change things. According to Professor Mike Duff, the math scientists use to apply string theory to black holes is exactly the same as the math that is used to describe quantum entanglement between three particles. In a paper published in this week's Physical Review Letters, Duff and his team of colleagues detail an experiment involving four entangled particles and predict the result based on the mathematics of string theory. If researchers can manage to carry out this experiment, and if the results agree with the team's predictions, string theory will finally have the experimental backing scientists have been seeking for decades.
Currently, there seems to be no practical connection between quantum entanglement and the string physics of black holes. Even Duff acknowledges that they are "unexpected and unrelated" areas of physics. Perhaps researchers are about to discover more than they bargained for. Or perhaps all of this is simply an odd, yet serendipitous, coincidence.
Thursday, August 26, 2010
When galaxies collide.
Thanks to science fiction, most people know that our universe is a dangerous place. If you happen to cross the event horizon of a black hole (which is invisible, by the way), your body will immediately be ripped to shreds by tidal forces, and every bit of matter that ever made you "you" will be crushed to an infinite density. In case that doesn't scare you, try this on for size: black holes exist at the center of many galaxies, including our own. That's right. 20,000 light years away, there is an enormously energetic, spectacularly dense, churning pit of doom just waiting for its next victim to wander one step too close. Supermassive black holes (SMBHs) fuel objects called quasars, which are some of the most powerful and luminous sources of radiation in the universe. Quasars can be detected from billions of light years away due to the extraordinary amounts of energy that SMBHs provide them with. But how did these black holes form in the first place?
Artist rendering of dust in the quasar wind. Image courtesy of NASA/JPL.
The SMBHs that power quasars were born when the universe was still very young, mere millions of years after the Big Bang. This means that they must have formed very quickly, and in an environment that contained very few metals. A metal-rich atmosphere would have given rise to normal stars, not black holes; however, even a metal-poor atmosphere would not have been able to yield such massive black holes in such a short time. Now, researchers from Ohio State University believe they have solved the problem. In a paper published in this week's Nature, they suggest that SMBHs formed during the collisions of protogalaxies in the early universe. According to their theory, SMBHs are created when two massive, orbiting galaxies collide and merge into one large, spinning disk of gas. As the gas swirls, it collects in the center of the disk and condenses under the influence of gravity. In only 10,000 years, this process creates a gas clump that weighs hundreds of millions of times the mass of our sun! Eventually, the clump becomes dense enough to create the precursor to a SMBH, or a "seed." This seed gathers more material over time, until it becomes one of the powerful and ancient black holes we observe today.
Artist's rendering of a supermassive black hole. Image courtesy of Phil Plait.
Of course, this mechanism can only explain the formation of SMBHs by colliding galaxies above a certain mass. The OSU team plans to further their research by surveying the masses of SMBHs at different distances, and thus different times in the past. (Since light from faraway stars always travels to us at a fixed rate, looking into the distant universe actually allows scientists to see the universe as it was billions and billions of years ago.) If they can back their model with observational evidence, the OSU team will be that much closer to understanding the complexities of stellar evolution.
Artist rendering of dust in the quasar wind. Image courtesy of NASA/JPL.
The SMBHs that power quasars were born when the universe was still very young, mere millions of years after the Big Bang. This means that they must have formed very quickly, and in an environment that contained very few metals. A metal-rich atmosphere would have given rise to normal stars, not black holes; however, even a metal-poor atmosphere would not have been able to yield such massive black holes in such a short time. Now, researchers from Ohio State University believe they have solved the problem. In a paper published in this week's Nature, they suggest that SMBHs formed during the collisions of protogalaxies in the early universe. According to their theory, SMBHs are created when two massive, orbiting galaxies collide and merge into one large, spinning disk of gas. As the gas swirls, it collects in the center of the disk and condenses under the influence of gravity. In only 10,000 years, this process creates a gas clump that weighs hundreds of millions of times the mass of our sun! Eventually, the clump becomes dense enough to create the precursor to a SMBH, or a "seed." This seed gathers more material over time, until it becomes one of the powerful and ancient black holes we observe today.
Artist's rendering of a supermassive black hole. Image courtesy of Phil Plait.
Of course, this mechanism can only explain the formation of SMBHs by colliding galaxies above a certain mass. The OSU team plans to further their research by surveying the masses of SMBHs at different distances, and thus different times in the past. (Since light from faraway stars always travels to us at a fixed rate, looking into the distant universe actually allows scientists to see the universe as it was billions and billions of years ago.) If they can back their model with observational evidence, the OSU team will be that much closer to understanding the complexities of stellar evolution.
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