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Black Holes Encyclopedia

NGC 4342

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In the constellation Virgo


75 million light-years (23 megaparsecs)


300 million times the mass of the Sun


Diameter equal to the diameter of Jupiter’s orbit around the Sun

Discovery Methods


NGC 4342

One of the key topics in black-hole research is the relationship between the mass of black holes at the centers of galaxies and the mass of the surrounding "bulges" of stars. Early research showed that the black hole was typically about 0.2 percent as massive as the bulge. Such a close correlation suggests that the black hole and bulge form together.

Yet not all black holes fit this ratio. The black hole at the center of NGC 4342, a lens-shaped galaxy in the Virgo Cluster, far exceeds this relationship. The black hole is roughly 300 million times the mass of the Sun. A 2012 study found that is about seven percent as massive as the bulge, putting it well out of line with the suspected black hole-bulge relationship.

One possible explanation for the discrepancy is an effect known as tidal stripping, in which stars and gas are pulled away from one galaxy by the gravitational pull of another galaxy. That would skew the ratio of the masses of the black hole and the bulge. It would also strip away much of the galaxy's surrounding "halo" of dark matter, which produces no detectable energy but exerts a gravitational pull on the visible matter around it.

To test that idea, astronomers used the space-based Chandra X-Ray Telescope to map superhot gas in and around NGC 4342. The X-ray-emitting gas traces the presence of dark matter around the galaxy's visible disk.

The observations showed that instead of a thinner dark-matter halo, which would be the result of tidal stripping, NGC 4342 has a relatively hefty halo. That seems to negate the idea of tidal stripping, suggesting that the formation of the black hole and bulge may follow different processes for some galaxies.


Black Hole Growth Found to be Out of Synch (Chandra X-Ray Observatory)
A study using Chandra X-Ray Observatory has found that the black hole in the center of NGC 4342 is heavier in relation to the surrounding bulge of stars than the black holes in most galaxies.


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This document was last modified: February 22, 2013.


NGC 4342
Ground-Based Photo

NGC 4342


No animations available for this black hole.