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A black hole in the nearby galaxy M32

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This animation (MPEG 4.8 Mb) shows the motions of stars caught in the gravitational field of a three-million solar mass black hole in the core of the nearby galaxy M32. Stars swarm around the black hole like angry bees around a hive.

The animation is based on computer simulations and new Hubble Space Telescope observations of M32. These were reported in the February 13, 1997 issue of Nature Magazine, by Roeland van der Marel (Institute for Advanced Study, Princeton, NJ) and co-investigators Tim de Zeeuw (Leiden University, The Netherlands), Hans-Walter Rix (University of Arizona) and Gerald Quinlan (Rutgers University, NJ). The team further includes Nicolas Cretton (Leiden University, The Netherlands), Steinn Sigurdsson (Cambridge University, UK) and Lars Hernquist (University of California at Santa Cruz). The calculations were done in part on the Cray T3D Parallel Supercomputer of the Pittsburgh Supercomputing Center.

Hubble's Faint Object Spectrograph was able to zoom in to the central light-year of M32, providing five times higher spatial resolving power than the best ground-based observations. The projected velocities of the stars in the galaxy were measured, and their three-dimensional motion was then reconstructed using state-of-the-art computer models. The observed velocities exceed those measured from previous ground-based observations, demonstrating that the stars must be attracted by an invisible black hole. In the absence of a black hole, the stars would move at a much slower rate, as shown in the animation.

M32 is a small companion galaxy of the great (full extent several times that of the full moon) spiral galaxy in the constellation of Andromeda. Because of its proximity, only 2.2 million light-years away, M32 has long been intensively studied with the best ground-based telescopes. The velocities of the stars near its nucleus suggested the presence of a black hole as early as 1984. In 1992, Hubble observations measured a bright peak, or `cusp' of starlight that independently suggested that the stars were concentrated around a black hole. The new Hubble measurements of the stellar motions have further strengthened the evidence for this.


cartoon of
stellar motions



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Last modified December 8, 1998.
Roeland van der Marel, marel@stsci.edu.
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