NGC 4486, Virgo A
in the constellation Virgo
6.6 billion times the mass of the Sun
Three times the diameter of Pluto's orbit around the Sun
The heart of the galaxy known as M87 is a place of unimaginable violence. A black hole up to seven billion times as massive as the Sun sits at the galaxy's center -- one of the most massive black holes ever measured. As gas spirals into the black hole, it's heated to millions of degrees, so it produces enormous amounts of X-rays. Some of the hot gas around the black hole shoots back into the galaxy in powerful jets that span thousands of light-years.
M87 is at the center of the Virgo Cluster, a collection of thousands of galaxies that move through space together. It is a giant elliptical galaxy, so it's shaped like a fat, fuzzy watermelon. M87's diameter is only a little bigger than the Milky Way's, but because the galaxy is thicker than the thin disk of the Milky Way, it encompasses a much larger volume. As a result, M87 contains many more stars and is perhaps 10 times as massive as the Milky Way.
Several lines of evidence suggest that M87's core contains a supermassive black hole. (In fact, it was one of the first galaxies suspected to have a black hole, based on observations conducted in the early 1980s.)
First, observations with Hubble Space Telescope revealed that the core contains staggering numbers of stars -- thousands of times more than astronomers would normally expect to see even in the crowded center of a galaxy. Hubble also detected clouds of gas orbiting the center of the galaxy at very high speeds. These clouds form a spiral pattern, like the shape of the Milky Way. The stars and gas clouds are probably pulled into the center of the galaxy by a compact, dense object -- like a supermassive black hole.
And second, both optical and radio telescopes reveal the jets of hot gas that shoot into space at 99 percent of the speed of light. The jets probably form as powerful magnetic fields focus some of the superhot material just outside the black hole into two beams. The jets hold together for about 6,000 light-years before they really begin to slow down and spread out. Eventually, the expanding, cooling gas forms two big bubbles that each span about 200,000 light-years -- twice the diameter of our own Milky Way galaxy.
A study of the galaxy published in 2009 concluded that M87's black hole is even bigger than astronomers had thought. While earlier studies put its mass at about three billion times that of the Sun, the new study determined that it is probably six billion to seven billions times the Sun's mass. The new study, conducted in part at McDonald Observatory, took into account the galaxy's dark matter, which affects the motions of stars within the galaxy. Incorporating that extra mass into the measurements of how fast the galaxy's stars are moving convinced the astronomers that M87's black hole is an even bigger monster than anyone had thought.
Texas Astronomers 'Weigh' Heaviest Known Black Hole (McDonald Observatory)
New observations show that the black hole at the center of the galaxy M87 is about 6.6 billion times as massive as the Sun, making it the most massive black hole in our cosmic neighborhood.
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This document was last modified: May 10, 2011.