Unexpected stellar velocity distribution in the warped Galactic disk
Article Abstract:
The gaseous disk of our Galaxy is warped, a phenomenon which has been detected in the distribution of luminous stars, galactic dust and molecular clouds. However there is no agreement as to how galactic disks become warped, although some theories suggest intergalactic winds, magnetic pressure and tidal interactions with satellites. A new study uses information from the Hipparcos satellite to detect the small stellar motions in the sky's plane that should occur with the warp. It is found that the spatial distribution of stars is in line with previous studies of hydrogen but the velocity distribution is contrary to that expected. A solution to the puzzle may help provide a reason for galactic warps.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1998
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Unstable by design
Article Abstract:
Burdier and colleagues have summarized work on quasar disk instabilities and have shown that the disk will be unstable even if irradiated from above. They have applied a global instability criterion to the outside edge of the accretion disk. Theorists have gone further than the physics of steady quasar disks by studying hydrogen ionization instability, but it was not clear that this instability applied to quasars.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1999
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