银河系介绍详细分析.ppt

* Eighteenth-century English astronomer William Herschel constructed this map of the Galaxy by counting the numbers of stars he saw in different directions in the sky. He assumed that all stars were of roughly equal luminosity and, within the confines of the Galaxy, were uniformly distributed in space. Our Sun (marked by the large yellow dot) appears to lie near the center of the distribution, and the long axis of the diagram lies in the plane of the Galactic disk. * /apod/ap960713.html Few stars are still forming in the old giant spiral galaxy M81. The blue regions in this picture - representing ultraviolet light - highlight regions of bright young stars and star formation and appear rare than in M74 and M33. The red regions - representing the visible light - show a large population of older, less massive stars. * A wide-angle far-infrared image of the disk and bulge of the Milky Way Galaxy, as observed by the Cosmic Background Explorer (COBE) satellite. * A photograph of stellar and interstellar matter in the direction of the Galactic center. Because of heavy obscuration, even the largest optical telescopes can see no farther than 1/10 the distance to the center. * /apod/ap970501.html * /photo/2002/gcenter/more.html * Detection of about 1,000 discrete X-ray sources (white dwarf stars, neutron stars, and black holes) Detection of large amounts of hot gas of tens of million degrees (heated and chemically enriched by frequent supernovae and escaping into the Galactic halo) Map of the fluorescent (reflected) X-ray radiation (tracing the radiation history of the central supermassive black hole) * /headlines/y2001/ast05sep_1.htm?list477791 * Frame (a) renders the Galaxys overall shape. The scale of this frame measures about 100 kpc from top to bottom. Frame (b) spans a distance of 10 kpc from top to bottom and is nearly filled by the great circular sweep of the innermost spiral arm. Moving in to a 1-kpc span, frame (c) depicts the 400-pc ring of matter mentioned ear