Subaru Telescope Spots Largest Structure In The Universe
Hilo HI (SPX) Jul 28, 2006
A team of astronomers using the Subaru and Keck telescopes on Mauna Kea has discovered a giant, three-dimensional filament of galaxies extending across 200 million light-years of space.
The filament, which apparently formed only 2-billion years after the Big Bang, is the largest structure ever discovered. It is studded with more than 30 large concentrations of gas, each up to 10 times as massive as the Milky Way galaxy.
Astronomers think the gas clouds are the progenitors of the most massive galaxies that exist in the present universe.
The finding is considered important, because it gives researchers new insight into the large-scale structure of the cosmos. Previously, astronomers expected the universe to look relatively smooth 2-billion years after the Big Bang.
"Something this large and this dense would have been rare in the early universe," said astronomer Ryosuke Yamauchi of Tohoku University in Japan. "The structure we discovered and others like it are probably the precursors of the largest structures we see today, which contain multiple clusters of galaxies."
The research group used the Subaru telescope to make a detailed study of a region of sky 12-billion light-years away known to have a large concentration of galaxies.
They used the Subaru Suprime-cam camera outfitted with special filters designed to be sensitive to the red-shifted light from galaxies at that distance. The results showed this concentration of galaxies is just a small portion of a much larger structure.
The newly found giant structure contains up to four times more galaxies than the universe's average for a space that large. The other known structures with such a high density are much smaller, measuring about 50-million light-years across.
Using Subaru's Faint Object Camera and Spectrograph to study the 3D distribution of galaxies in the filament, the team also discovered at least three overlapping filaments that make up the giant structure.
Astronomers knew this region contained at least two large concentrations of gas, one of them extending across 400,000 light-years, or more than four times the diameter of the Milky Way.
The researchers found these large concentrations of gas are located near the overlap regions of the filaments.
The Subaru observations also found much fainter objects than previously discovered in the region. For example, they found 33 new large concentrations of gas along the filamentary structure extending across 100,000 light-years.
This is the first time so many large concentrations of gas, known to astronomers as Lyman alpha blobs, have been discovered in the distant universe.
Astronomers think such Lyman alpha blobs - named because since they are seen in the Lyman alpha emission line of hydrogen - are probably related to the births of the largest galaxies.
In the gravitational-heating model of astrophysics, the blobs are regions where gas is collapsing under its own gravity to form a galaxy. In the photo-ionization model, emissions from the gas result from the ionization by ultraviolet light from newborn stars or a massive black hole.
The shock-heating and galactic-superwind models hypothesize that the glow of the gas is caused by the death of many massive stars born early in the history of the universe. They lived out their short lives, then died in supernova explosions that blew out surrounding gas.
Team members Yoshiaki Taniguchi and Yasuhiro Shioya of Ehime University in Japan have been advocating the galactic-superwind model.
Observations with the DEIMOS spectrograph at the Keck II telescope revealed the gas inside the blobs moves with speeds greater than 500 kilometers (300 miles) per second, or more than 1-million miles per hour.
The extent of the gas concentrations and the speed of the material within them suggest these regions must be up to 10 times more massive than the Milky Way.
The blobs show a great variety in shape and brightness. For example, some show bubble-like features that match computer simulations of galactic winds. There also are diffuse blobs and those consisting of several galaxies.
"Galaxies of various sizes surround us," said Yuichi Matsuda of Kyoto University in Japan. "The large gas concentrations we found may tell us a lot about how the largest of these came to be."
The research was published in a series of research papers in the Astronomical Journal and the Astrophysical Journal.
Vibro-Acoustic Tests On Webb Telescope Primary Mirror Completed
Redondo Beach CA (SPX) Jul 25, 2006
In an ongoing demonstration of the technological readiness of the James Webb Space Telescope, a team led by Northrop Grumman and Ball Aerospace successfully completed several rigorous tests that proved the primary mirror for the telescope can successfully withstand launch and function as planned in its space environment.
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