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Is there any Dark Matter in 2011 Quadrantid Meteors star shower???From: STALKER2002
Subject: General
Date/Time 2011-01-14 15:26:38
Remote IP: 188.123.240.114
Messagehttp://www.sciencedaily.com/releases/2011/01/110113131425.htm
New Technique Could Pinpoint 'Galaxy X': Satellite Galaxies Located Based on the Ripples They Create in the Hydrogen Gas
ScienceDaily (Jan. 14, 2011) — Planet X, an often-sought 10th planet, is so far a no-show, but Sukanya Chakrabarti has high hopes for finding what might be called Galaxy X -- a dwarf galaxy that she predicts orbits our Milky Way Galaxy.
Many large galaxies, such as the Milky Way, are thought to have lots of satellite galaxies too dim to see. They are dominated by "dark matter," which astronomers say makes up 85 percent of all matter in the universe but so far remains undetected.
Chakrabarti, a post-doctoral fellow and theoretical astronomer at the University of California, Berkeley, has developed a way to find "dark" satellite galaxies by analyzing the ripples in the hydrogen gas distribution in spiral galaxies. Planet X was predicted -- erroneously -- more than 100 years ago based on perturbations in the orbit of Neptune.
Earlier this year, Chakrabarti used her mathematical method to predict that a dwarf galaxy sits on the opposite side of the Milky Way from Earth, and that it has been unseen to date because it is obscured by the intervening gas and dust in the galaxy's disk. One astronomer has already applied for time on the Spitzer Space Telescope to look in infrared wavelengths for this hypothetical Galaxy X.
"My hope is that this method can serve as a probe of mass distribution and of dark matter in galaxies, in the way that gravitational lensing today has become a probe for distant galaxies," Chakrabarti said.
Since her prediction for the Milky Way, Chakrabarti has gained confidence in her method after successfully testing it on two galaxies with known, faint satellites. She reported the details of these tests during an oral presentation on Jan. 13, 2011, during a meeting of the American Astronomical Society in Seattle, Wash.
"This approach has broad implications for many fields of physics and astronomy -- for the indirect detection of dark matter as well as dark-matter dominated dwarf galaxies, planetary dynamics, and for galaxy evolution driven by satellite impacts," she said.
Chakrabarti's colleague Leo Blitz, a UC Berkeley professor of astronomy, said that the method could also help test an alternative to dark matter theory, which proposes a modification to the law of gravity to explain the missing mass in galaxies.
"The matter density in the outer reaches of spiral galaxies is hard to explain in the context of modified gravity, so if this tidal analysis continues to work, and we can find other dark galaxies in distant halos, it may allow us to rule out modified gravity," he said.
The Milky Way is surrounded by some 80 known or suspected dwarf galaxies that are called satellite galaxies, even though some of them may just be passing through, not captured into orbits around the galaxy. The Large and Small Magellanic Clouds are two such satellites, both of them irregular dwarf galaxies.
Theoretical models of rotating spiral galaxies, however, predict that there should be many more satellite galaxies, perhaps thousands, with small ones even more prevalent than large ones. Dwarf galaxies, however, are faint, and some of the galaxies may be primarily invisible dark matter.
Chakrabarti and Blitz realized that dwarf galaxies would create disturbances in the distribution of cold atomic hydrogen gas (H I) within the disk of a galaxy, and that these perturbations could reveal not only the mass, but the distance and location of the satellite. The cold hydrogen gas in spiral galaxies is gravitationally confined to the plane of the galactic disk and extends much farther out than the visible stars -- sometimes up to five times the diameter of the visible spiral. The cold gas can be mapped by radio telescopes.
"The method is like inferring the size and speed of a ship by looking at its wake," said Blitz. "You see the waves from a lot of boats, but you have to be able to separate out the wake of a medium or small ship from that of an ocean liner."
The technique Chakrabarti developed involves a Fourier analysis of the gas distribution determined by high-resolution radio observations. Her initial predication of Galaxy X around the Milky Way was made possible by a wealth of data already available on the atomic hydrogen in our galaxy. To test her theory on other galaxies, she and her collaborators used recent data from a radio survey called The HI Nearby Galaxy Survey (THINGS), conducted by the Very Large Array, as well as its extension to the Southern Hemisphere, THINGS-SOUTH, a survey carried out by the Australia Telescope Compact Arra
http://www.sciencedaily.com/releases/2011/01/110113131425.htm
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