| Sneakeh Cat | 02-07-2009 07:00 PM |
Reese walked up to the Astronomy Tower and glanced at the bulletin board full of articles.After reading a few,she pulled out three articles she had found and pinned them up: Quote:
1.5.09
Data Uncover Bigger Galaxy in Cosmos, and It’s Ours
It turns out that Andromeda, previously thought to be the biggest galaxy in this part of the universe, may not have bragging rights over the Milky Way after all.
Astronomers said Monday that the Milky Way is more massive than earlier known, given new measurements showing that the Sun is moving at 600,000 miles per hour around the center of the galaxy, or 100,000 m.p.h. faster than past calculations suggested.
The higher speed of the Sun means the galaxy must have more mass — about 50 percent more — so as to generate a stronger gravitational pull to keep hold of the Sun, as well as all its other stars. That expands the Milky Way to roughly the heft of Andromeda.
“We thought we were like a little sister of Andromeda,” said a member of the research team, Mark J. Reid, an astronomer at the Harvard-Smithsonian Center for Astrophysics. “Now we’re like fraternal twins.”
Determining the shape, size and mass of the Milky Way is difficult. Most of the mass is in the form of invisible dark matter, a component that far outweighs the ordinary matter in stars and gas clouds.
The astronomers, who reported their findings in Long Beach, Calif., at a meeting of the American Astronomical Society, used the Very Long Baseline Array, a system of 10 radio telescopes stretching from Hawaii to the Virgin Islands. The team looked at bright, star-forming regions within the Milky Way, then measured the motion of those regions against the background of far more distant objects as the Milky Way rotated.
In a second finding, another team of astronomers found something surprising at the center of the Milky Way: baby stars, still in the process of coalescing out of dust and gas.
Astronomers have known of young stars near the gigantic black hole at the center of the Milky Way, some 28,000 light-years from Earth, but there has been a mystery as to how they got there. The tidal forces induced by the black hole would rip gas clouds to shreds before they could coalesce and collapse into stars, astronomers believed. Yet it also seemed unlikely that so many stars would have formed elsewhere and then pulled inward.
Using a radio telescope array in New Mexico, Elizabeth M. L. Humphreys, a Harvard-Smithsonian astronomer, and her colleagues have now discovered two protostars — baby stars still in their cocoons of dust and gas — within a few light-years of the black hole.
The astronomers said that the gas clouds appeared to be 10 to 1,000 times denser than typical star-forming clouds and that this helped hold them together against the tidal forces.
Article Found Here:New York Times
| Quote:
1.7.09
Theory Ties Radio Signal to Universe’s First Stars
When the universe was still young, they were already dying.
The first stars ever to grace the cosmos with light were brutish monsters, so the story believed by most astronomers goes, lumbering clouds of hydrogen and helium hundreds of times more massive than the Sun. They lived fast and bright and died hard, exploding or collapsing into massive black holes less than a billion years after the Big Bang, never to be seen again.
But they might have left something behind, a buzz of radio waves emitted by high-energy particles spit from the doomed gas swirling around those black holes.
Has that buzz, a cry from the vanished ancestors of our Sun, now been heard?
That is at least one “wildly speculative” explanation, said Alan Kogut of the Goddard Space Flight Center, for a mysterious radio static that seems to pervade the universe. He led a team that discovered the signal accidentally while scanning the skies in July 2006 with a set of sensitive radio receivers called Arcade lofted 21 miles high on a balloon.
The signal manifests itself as a puzzling excess at certain frequencies of a fog of microwaves that permeates the cosmos and is probably left over from the Big Bang itself. It suggests that something is pumping large amounts of extra energy — about six times more than can be accounted for by all the galaxies known and unknown — into the universe.
“It came as a big surprise to us,” Dr. Kogut said. His colleague, Michael D. Seiffert of the Jet Propulsion Laboratory, said, “It’s exciting new evidence of something new and exciting going on in the universe.”
In an interview, four papers submitted to the Astrophysical Journal and a press conference Wednesday at a meeting of the American Astronomical Society in Long Beach, Calif., Dr. Kogut and his colleagues stressed that they do not really know where the signal comes from and they hope that theorists will take up the quest. They have been careful mainly to explain what the signal is not, namely distant galaxies or decaying particles of exotic dark matter.
The idea that the radio signal originates with black holes from the first stars is therefore alluring.
“If the Arcade result is linked to that epoch,” Dr. Kogut said, “it is one of very few probes we have of what went on when the very first stars are forming.”
Other astronomers were scratching their heads, reserving judgment until they could digest the data. Dr. Kogut has a reputation for being very careful, they said, and his results are sure to spark debate. David Spergel of Princeton University, an expert on cosmic radiation, said that Dr. Kogut’s results seemed reasonably solid. “It’s intriguing,” he said. “We’re seeing something we hadn’t expected to see.”
The interpretation, he added, is unclear.
Neal Weiner, an astrophysicist at New York University, said in an e-mail message that the idea that the signal came from black holes around the first generation of stars “would be cool.”
“Early black holes are generally cool!” he wrote.
Astronomers have been scrutinizing the fog, known as the cosmic microwave background, since 1965 when it was accidentally discovered by Arno Penzias and Robert Wilson of Bell Laboratories, who later won a Nobel prize. Over the years, a variety of measurements have shown that the spectrum of the cosmic radiation conforms to the idealized pattern of a so-called black body with a temperature of 2.7 degrees Kelvin. That is 2.7 degrees above absolute zero, which is minus 459.6 degrees Fahrenheit.
Dr. Kogut’s experiment, a set of seven antennas called Arcade, for Absolute Radiometer for Cosmology, Astrophysics and Diffuse Emission, was able to observe this fog precisely in a part of the spectrum with wavelengths of a few centimeters that had not been well studied before. That band, Dr. Kogut explained, falls between shorter wavelengths studied by satellites like NASA’s Cosmic Background Explorer and longer ones accessible to ground-based radio telescopes.
To prevent heat from the Earth’s atmosphere or anything else from contaminating the delicate measurements, the entire instrument array sits in what Dr. Kogut called “a flying cold tub.” That is literally a giant bucket, open at the top and filled with superfluid liquid helium, which cools the antennas to the same temperature as the universe, 2.7 degrees, generating five cubic meters of gas per second.
Arcade was designed to look for small deviations from the black body shape that might represent the onset of star formation, which would have added heat to the universe, or the decay of the hypothetical dark matter particles that make up 25 percent of nature and that form the scaffolding for galaxies. What they saw during a four-hour flight out of Palestine, Tex., in 2006 — after surveying about 7 percent of the sky and laboriously filtering out the booming radio presence of our own Milky Way galaxy — was much bigger than that.
“What the heck is this?” Dr. Kogut remembered exclaiming when he first saw the data. “This shouldn’t be here.”
They spent the next year, he recalled, trying to make the excess go away, but finally convinced themselves they had not made any mistakes.
The spectrum of the extra radiation, Dr. Kogut said, is consistent with that produced by radio galaxies, of particles spiraling in a magnetic field. But radio galaxies also produce a lot of infrared heat radiation from dust, and astronomers do not see enough infrared waves to account for a new bunch of galaxies.
“Whatever is producing the signal,” he said, “is not producing a lot of infrared emission.”
But the ratio of radio to infrared emission is not so well known, pointed out Dr. Spergel, who said that one plausible explanation — perhaps the most conservative one — is that supernovas and black holes in young star-forming galaxies are simply putting out more radio radiation than had been thought.
But another possibility, he agreed, is Dr. Kogut’s speculation that the new signal comes from a time before the universe produced any dust. Dust grows over time as stars manufacture heavy elements called metals, like carbon, silicon and oxygen, that make up dust and then spit them out into space.
Astronomers know of two classes of stars today: so-called Population 1 stars like the Sun, which are relatively well evolved chemically, and an older group known as Population 2, which are smaller, redder, older and less well-endowed with heavier elements. But they have long speculated that there was a lost generation, so-called Population 3 stars, which first formed out of pure hydrogen and helium produced in the Big Bang and got the whole show going.
The lives and properties of these stars, as Dr. Kogut said, have been the subject of active debate, but their collapse into black holes could produce the requisite radio excess without any accompanying dust radiation. Any dust those stars had produced would be very sparse and probably far out in space away from the hole and the jets.
“That is the mental picture I’m carrying around,” Dr. Kogut said. “But I emphasize that this interpretation is just speculation at present — no one has yet done any real calculations to see if this holds up under closer scrutiny or not.”
Correction: A previous version of this article misstated the rate at which superfluid liquid helium evaporates to cool the antennas. The evaporation generates five cubic meters of gas per second; it does not evaporate at the rate of five cubic meters per second.
Article Found Here:New York Times
| Quote:
1.7.09
Theory Ties Radio Signal to Universe’s First Stars
When the universe was still young, they were already dying.
The first stars ever to grace the cosmos with light were brutish monsters, so the story believed by most astronomers goes, lumbering clouds of hydrogen and helium hundreds of times more massive than the Sun. They lived fast and bright and died hard, exploding or collapsing into massive black holes less than a billion years after the Big Bang, never to be seen again.
But they might have left something behind, a buzz of radio waves emitted by high-energy particles spit from the doomed gas swirling around those black holes.
Has that buzz, a cry from the vanished ancestors of our Sun, now been heard?
That is at least one “wildly speculative” explanation, said Alan Kogut of the Goddard Space Flight Center, for a mysterious radio static that seems to pervade the universe. He led a team that discovered the signal accidentally while scanning the skies in July 2006 with a set of sensitive radio receivers called Arcade lofted 21 miles high on a balloon.
The signal manifests itself as a puzzling excess at certain frequencies of a fog of microwaves that permeates the cosmos and is probably left over from the Big Bang itself. It suggests that something is pumping large amounts of extra energy — about six times more than can be accounted for by all the galaxies known and unknown — into the universe.
“It came as a big surprise to us,” Dr. Kogut said. His colleague, Michael D. Seiffert of the Jet Propulsion Laboratory, said, “It’s exciting new evidence of something new and exciting going on in the universe.”
In an interview, four papers submitted to the Astrophysical Journal and a press conference Wednesday at a meeting of the American Astronomical Society in Long Beach, Calif., Dr. Kogut and his colleagues stressed that they do not really know where the signal comes from and they hope that theorists will take up the quest. They have been careful mainly to explain what the signal is not, namely distant galaxies or decaying particles of exotic dark matter.
The idea that the radio signal originates with black holes from the first stars is therefore alluring.
“If the Arcade result is linked to that epoch,” Dr. Kogut said, “it is one of very few probes we have of what went on when the very first stars are forming.”
Other astronomers were scratching their heads, reserving judgment until they could digest the data. Dr. Kogut has a reputation for being very careful, they said, and his results are sure to spark debate. David Spergel of Princeton University, an expert on cosmic radiation, said that Dr. Kogut’s results seemed reasonably solid. “It’s intriguing,” he said. “We’re seeing something we hadn’t expected to see.”
The interpretation, he added, is unclear.
Neal Weiner, an astrophysicist at New York University, said in an e-mail message that the idea that the signal came from black holes around the first generation of stars “would be cool.”
“Early black holes are generally cool!” he wrote.
Astronomers have been scrutinizing the fog, known as the cosmic microwave background, since 1965 when it was accidentally discovered by Arno Penzias and Robert Wilson of Bell Laboratories, who later won a Nobel prize. Over the years, a variety of measurements have shown that the spectrum of the cosmic radiation conforms to the idealized pattern of a so-called black body with a temperature of 2.7 degrees Kelvin. That is 2.7 degrees above absolute zero, which is minus 459.6 degrees Fahrenheit.
Dr. Kogut’s experiment, a set of seven antennas called Arcade, for Absolute Radiometer for Cosmology, Astrophysics and Diffuse Emission, was able to observe this fog precisely in a part of the spectrum with wavelengths of a few centimeters that had not been well studied before. That band, Dr. Kogut explained, falls between shorter wavelengths studied by satellites like NASA’s Cosmic Background Explorer and longer ones accessible to ground-based radio telescopes.
To prevent heat from the Earth’s atmosphere or anything else from contaminating the delicate measurements, the entire instrument array sits in what Dr. Kogut called “a flying cold tub.” That is literally a giant bucket, open at the top and filled with superfluid liquid helium, which cools the antennas to the same temperature as the universe, 2.7 degrees, generating five cubic meters of gas per second.
Arcade was designed to look for small deviations from the black body shape that might represent the onset of star formation, which would have added heat to the universe, or the decay of the hypothetical dark matter particles that make up 25 percent of nature and that form the scaffolding for galaxies. What they saw during a four-hour flight out of Palestine, Tex., in 2006 — after surveying about 7 percent of the sky and laboriously filtering out the booming radio presence of our own Milky Way galaxy — was much bigger than that.
“What the heck is this?” Dr. Kogut remembered exclaiming when he first saw the data. “This shouldn’t be here.”
They spent the next year, he recalled, trying to make the excess go away, but finally convinced themselves they had not made any mistakes.
The spectrum of the extra radiation, Dr. Kogut said, is consistent with that produced by radio galaxies, of particles spiraling in a magnetic field. But radio galaxies also produce a lot of infrared heat radiation from dust, and astronomers do not see enough infrared waves to account for a new bunch of galaxies.
“Whatever is producing the signal,” he said, “is not producing a lot of infrared emission.”
But the ratio of radio to infrared emission is not so well known, pointed out Dr. Spergel, who said that one plausible explanation — perhaps the most conservative one — is that supernovas and black holes in young star-forming galaxies are simply putting out more radio radiation than had been thought.
But another possibility, he agreed, is Dr. Kogut’s speculation that the new signal comes from a time before the universe produced any dust. Dust grows over time as stars manufacture heavy elements called metals, like carbon, silicon and oxygen, that make up dust and then spit them out into space.
Astronomers know of two classes of stars today: so-called Population 1 stars like the Sun, which are relatively well evolved chemically, and an older group known as Population 2, which are smaller, redder, older and less well-endowed with heavier elements. But they have long speculated that there was a lost generation, so-called Population 3 stars, which first formed out of pure hydrogen and helium produced in the Big Bang and got the whole show going.
The lives and properties of these stars, as Dr. Kogut said, have been the subject of active debate, but their collapse into black holes could produce the requisite radio excess without any accompanying dust radiation. Any dust those stars had produced would be very sparse and probably far out in space away from the hole and the jets.
“That is the mental picture I’m carrying around,” Dr. Kogut said. “But I emphasize that this interpretation is just speculation at present — no one has yet done any real calculations to see if this holds up under closer scrutiny or not.”
Correction: A previous version of this article misstated the rate at which superfluid liquid helium evaporates to cool the antennas. The evaporation generates five cubic meters of gas per second; it does not evaporate at the rate of five cubic meters per second.
Article Found Here:New York Times
| After pinning up all the articles,Reese exited the Atronomy Tower. |
