M84
The cores of galaxies are among the most turbulent and exciting regions in the modern universe. They teem with massive stars, rippling magnetic fields, and supermassive black holes that surround themselves with disks of superhot gas.
An example is the galaxy M84. It's a member of the Virgo Cluster -- hundreds of galaxies that travel through space as a unit, bound by their mutual gravity. Virgo is easy to find tonight because it rises below the Moon. Look for the brilliant planet Jupiter below the Moon, and Virgo's brightest star, Spica, below Jupiter.
M84 has been classified as an elliptical galaxy, which means that it looks like a fuzzy football. In recent years, though, some astronomers have suggested that it's a "lenticular" galaxy -- one that looks like a disk when seen from above, but a lens when seen from the side. In either case, M84 is larger and more massive than our own galaxy, the Milky Way.
In 1997, Hubble Space Telescope revealed that gas about 25 light-years from the center of M84 is orbiting at very high speeds. Only the gravitational pull of a supermassive black hole could account for this motion.
Early estimates said the black hole must be at least 300 million times as massive as the Sun. With continued observations, though, astronomers have raised the estimate to about one and a half billion times the mass of the Sun. That makes the black hole in M84 one of the largest and most massive yet discovered.
Script by Damond Benningfield, Copyright 2005
For more information, visit StarDate's Black Holes Encyclopedia.
For more skywatching tips, astronomy news, and much more, read StarDate magazine.
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