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Black Holes Encyclopedia

NGC 1023

Printable version




in the constellation Perseus

Finder Chart


33 million light-years (11.4 megaparsecs)


40 million to 60 million times the mass of the Sun


Roughly the size of Earth's orbit around the Sun

Discovery Methods


NGC 1023

NGC 1023 is classified as a "SB0" galaxy, which means that it has a disk shape and a central bulge of stars like our own Milky Way galaxy, but no spiral arms in the disk. Observations of this galaxy provide a good example of how space telescopes and ground-based telescopes can work together.

Astronomers pointed Hubble Space Telescope at the central region of NGC 1023 to collect detailed photographs of how stars are distributed in the galaxy's core. They also used one of Hubble's instruments to measure the combined spectrum of all the stars in an 8,000-light-year slice through the center.

These observations provided excellent measurements of the densest parts of the galaxy, but the astronomers also needed information about the outer regions, where stars are more spread out. They used telescopes in Arizona to take images and spectra covering a region 50,000 light years in size.

Then, by combining and comparing these "big-picture" measurements with the Hubble observations, they created a series of computer simulations of the galaxy, trying to match the their models of how the stars were distributed to the real distribution. The simulations with a black hole mass between 40 million and 60 million solar masses did the best job of imitating the real galaxy, so they concluded that the real black hole must have a mass of this size.

The Hubble spectra of NGC 1023 also showed evidence that some of the stars closest to the central black hole form a small flattened disk, instead of whirling about in random directions like most of the other stars in the galaxy's central bulge. Some of the stars in the disk are moving as fast as 1.3 million miles per hour, but even at this extreme speed, they are still unable to escape from the powerful gravity of the black hole.


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This document was last modified: March 15, 2012.


NGC 1023
Ground-Based Photo


No animations available for this black hole.