in the constellation Virgo
500 million to 1.2 billion times the mass of the Sun
Diameter range from the size of Saturn's orbit around the Sun to the size of Neptune's orbit
NGC 4261 is a giant elliptical galaxy in the Virgo cluster, a collection of thousands of galaxies that are bound to each other by their mutual gravitational pull.
Soon after it entered orbit, Hubble Space Telescope snapped some pictures of the center of the galaxy to test its camera system. Astronomers selected NGC 4261 because they considered it an "average" galaxy where not much was happening.
Even with its flawed mirror, though, Hubble found that the center of NGC 4261 is an extraordinary region. It appears to contain a supermassive black hole at least a half-billion times as massive as the Sun. A disk of cold, dark dust about 800 light-years wide encircles the black hole. Both the black hole and the disk are offset from the center of the galaxy by about 20 light-years, which is unusual.
At the inner edge of the disk, the material begins to heat up as the black hole's gravity pulls it ever closer. Some of this material falls into the black hole. But some of it, perhaps driven by powerful magnetic fields, shoots back into space at almost the speed of light. This material forms two "jets" that appear to come from the magnetic poles of the black hole. They don't come out of the black hole itself, but from the inner region of the accretion disk. These jets of particles and radiation span about 90,000 light-years -- a distance almost equal to the diameter of our own Milky Way galaxy.
Observations with the Chandra X-Ray Observatory show a trail of less-massive black holes and neutron stars through the outer regions of the galaxy. These objects may have formed as the result of a merger between NGC 4261 and another galaxy. As the smaller galaxy fell into the body of NGC 4261, big clouds of dust and gas rammed together. They eventually fragmented, with blobs of material forming massive stars. These stars quickly exploded, leaving behind only neutron stars or black holes.
There is some speculation that the central black hole is being fed by some of the remaining gas and dust from the galaxy that NGC 4261 cannibalized.
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This document was last modified: November 19, 2009.