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Galactic Center The galactic disc, which bulges outward at the galactic center, has a diameter of between 70,000 and 100,000 light-years. The distance from the Sun to the galactic center is now estimated at 26,000 ± 1400 light-years, while older estimates could put the Sun as far as 35,000 light-years from the central bulge.The galactic center harbors a compact object of very large mass as determined by the motion of material around the center. The intense radio source named Sagittarius A*, thought to mark the center of the Milky Way, is newly confirmed to be a supermassive black hole. Most galaxies are believed to have a supermassive black hole at their center.	0	0
Spiral Arms Each spiral arm describes a logarithmic spiral (as do the arms of all spiral galaxies) with a pitch of approximately 12 degrees. Outside of the major spiral arms is the Outer Ring or Monoceros Ring, a ring of stars around the Milky Way, which consists of gas and stars torn from other galaxies billions of years ago. Scutum-Crux Arm, Carina and Sagittarius Arm, Orion-Cygnus Arm, Norma and Outer Arm, 3-kpc and Perseus Arm	1	1	Wed Feb 03, 2010 7:05 am Admin
Spheroid Halo The galactic disk is surrounded by a spheroid halo of old stars and globular clusters, of which 90% lie within 100,000 light-years, suggesting a stellar halo diameter of 200,000 light-years. However, a few globular clusters have been found farther, such as PAL 4 and AM1 at more than 200,000 light-years away from the galactic center. While the disk contains gas and dust which obscure the view in some wavelengths, the spheroid component does not. Active star formation takes place in the disk (especially in the spiral arms, which represent areas of high density), but not in the halo. Open clusters also occur primarily in the disk.	0	0