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R. Genzel (Max Planck Institute for Extraterrestrial Physics& Physics Dept., UC Berkeley)
New observations with the NAOS/CONICA adpative optics camera at the ESO VLT in combination with 10 years of speckle imaging on the ESO NTT have now provided the first determinations of stellar orbits in the central arcsecond of the Milky Way. The center of gravity of these orbits is coincident with the radio position of SgrA*. Several stars are on highly elliptical orbits around SgrA*, with periods between 15 and a few hundred years. The star S2 went through its peri-approach in spring 2002 at which point it was a mere 17 light hours from the radio source and traveled at 8000 km/s. The Kepler orbits provide a precise tool for determining the gravitational potential, which is dominated by a three million solar mass, object to scales of a few light hours. We show that this mass concentration must be a central black hole, beyond reasonable doubt. The new data also constrain the properties of the stellar cusp arond the hole and demonstrate the unusual properties of the nuclear star cluster.
Bulletin of the American Astronomical Society,
© 2003. The American Astronomical Soceity.