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Black Holes Encyclopedia


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Alternate Names

NGC 221




in the constellation Andromeda

Finder Chart


2.4 million light-years (0.81 megaparsecs)


3 million times the mass of the Sun


Diameter about 10 million miles -- about 12 times the diameter of the Sun

Discovery Methods



M32 is a minor member of the Local Group, a collection of about three dozen galaxies (including the Milky Way) that is bound together by gravity. M32 orbits the much larger galaxy M31, which is the largest member of the Local Group.

M32 is classified as a dwarf elliptical galaxy. It looks like a fuzzy football, and spans about 8,000 light-years (compared to 100,000 light-years for the Milky Way).

Measurements with Hubble Space Telescope and telescopes on the ground show that stars in the nucleus of M32 are orbiting the center of the galaxy at very high speeds. This indicates that the stars are orbiting an object that is both compact and quite heavy: a supermassive black hole.

The black hole is surrounded by millions of stars that are densely packed. Anyone standing on a planet in this region of the galaxy would see a brilliant sky around the clock, and never truly experience "night."

M32's central black hole is in a "quiet" stage, which means that it is pulling in very little gas and dust. As a result, there is no major accretion disk of hot gas encircling the black hole.

Although M32 is too small and faint to see with the unaided eye, it is clearly visible in small telescopes or good binoculars. It looks like an elongated puffball at the edge of the more prominent M31.



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This document was last modified: November 19, 2009.


M32 and M31
Ground-Based Photo

M32 Hubble
Space-Based Photo


Stars Orbiting M32
Animation of stars orbiting the black hole in M32.