Milky Way, the galaxy of which the sun and solar system are a part, seen as a broad band of light arching across the night sky from horizon to horizon; if not blocked by the horizon, it would be seen as a circle around the entire sky. Although its motion is not readily apparent, the entire galaxy is rotating about the Milky Way's center. Relative to the universe, the galaxy is moving at a speed of c.370 mi per sec (c.590 km per sec) in the same direction that the constellation Leo lies relative to the earth; it is also moving at c.60 mi per sec (c.100 km per sec) relative to the center of mass of the local group of galaxies. The sun, traveling at a speed of c.150 mi per sec (c.240 km per sec) in a nearly circular orbit, takes 200–230 million years to complete one revolution.
since, The Milky Way is a large galaxy comprising an estimated 200 billion stars (some estimates range as high as 400 billion) arrayed in the form of a disk, with a central elliptical bulge (some 12,000 light-years in diameter) of closely packed stars lying in the direction of Sagittarius. It is surrounded by a flat disk marked by six spiral arms—four major and two minor—which wind out from the nucleus like a giant pinwheel. Because of these arms, the Milky Way was classified as a spiral galaxy. However, increasing evidence indicates that the Milky Way probably has a bar or barlike structure of new, bright stars in its central region. This would modify its classification to a barred spiral or an intermediate type between barred and “normal” spiral. Our sun is situated in one of the smaller arms, called the Local or Orion Arm, that connect the more substantial next inner arm and the next outer arm. The sun lies roughly two thirds of the way from the center of the disk, which is some 28,000 light-years distant, and in the galactic plane. When we look in the plane of the disk we see the combined light of its stars as the Milky Way. The diameter of the disk is c.100,000 light-years; its average thickness is 10,000 light-years, increasing to 30,000 light-years at the nucleus.
so it is moving at a normal speed with its arms moving a bit slower then the center as it needs more area to cover
2006-07-19 02:13:59
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answer #1
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answered by Explorer 5
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The outer arms of the Galaxy move around the centre at about 220-250 kms/sec.....about the same velocity as the Sun does, maybe just a bit faster. It does this because of the amount of mass which lies outside the Sun's orbit. The rotation curve of the Galaxy level's off and even rises a bit outside the Sun's orbit.
2006-07-19 10:28:56
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answer #2
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answered by ozzie35au 3
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