Galaxies Outside Milky Way Also Have Thick Disks |
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Written by spacetravel.org
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Friday, 20 May 2005 20:13 |
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The Milky Way has two concentric, overlapping disks: a dusty, gaseous thin disk that closely hugs the midplane and a thick disk, tens of thousands of light-years wide, consisting of old stars. Astronomers have now found that the Milky Way is not the only galaxy with a thick disk of old stars. Anil Seth of the University of Washington and two colleagues used the Hubble Space Telescopes Advanced Camera for Surveys to study a half dozen nearby edge-on spiral galaxies, and found that for every galaxy, thickness increased with the age of stars. The older a star, the further it tends to lie from the galaxys midplane. Jeremy R. Mould of the National Optical Astronomy Observatory has found extended disks populated by red stars in four other edge-on spirals. The Spitzer Space Telescope has identified a diffuse glow around NGC 5907, an 11th magnitude spiral in the constellation Draco. Matthew L.N. Ashby of the Harvard-Smithsonian Center for Astrophysics and his team have identified this glow as a thick disk made up very red stars.
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