About 300 million light years away from earth in the Coma Cluster is the elliptical Galaxy NC 4889, described by many as a “quiet” galaxy of sorts. However, lying within that galaxy is also one of the largest black holes that we have discovered to date.
When the Hubble Space Telescope released photos of NC 4889 last week, along came with it the discovery of a supermassive black hole at its center. While it’s impossible to directly observe a black hole, scientists used instruments at the Keck II Observatory and the Gemini Telescope in order to measure the velocity at which stars were moving around the center of the galaxy. Through these measurements, astronomers were able to figure out the extraordinary mass of the black hole.
To give you an idea of how large this black hole actually is, the black hole at the center of our galaxy has a mass that is only about 4 million of that of our sun, with an event horizon that’s only one-fifth the size of Mercury. To drive the comparison home, the black hole at the center of our galaxy is the largest object within the Milky Way. The black hole at the center of NC 4889 has a mass which is about 21 billion times than that of our sun and its event horizon is around 130 kilometers, which is about 15 times the diameter orbit of Neptune around the sun.
Now, I know what you’re thinking: “Ash, how on earth is this galaxy quiet? That black hole is huge!” Well yes, it is. However, there’s a pretty good chance that at this juncture it’s essentially a sleeping giant in our universe.
While, in its past, this black hole would have spent its time swallowing up stars and other objects in in the past, astronomers believe that the black hole is no longer feeding. This means that as of right now, it’s not active. In fact, the black hole is so quiet that stars have begun to form nearby the black hole completely and totally undisturbed by its presence.
During the black hole’s active period, NC 4889 would have been classified by astronomers as a quasar, and the massive black hole at its center would have emitted about 1,000 times the energy output than that of the Milky Way; astronomers are still detecting X-Ray emissions from said black hole that reach far beyond NC 4889.
For more information about this discovery, feel free to check out these links:
https://www.spacetelescope.org/news/heic1602/
http://www.iflscience.com/hubble-takes-new-look-gigantic-black-hole-and-its-quiet-host