• The circle shows a point-like source on the northern outskirts of the galaxy that may be associated with the black hole. (NASA/STScI)Source: NASA/STScI
Usually a big black hole stays in the centre of a galaxy - but not this one.
Signe Dean

7 Oct 2016 - 2:12 PM  UPDATED 7 Oct 2016 - 2:12 PM

Supermassive black holes, the kind that can be up to ten billion times more massive than our Sun, are theorised to be at the centre of most large galaxies. That includes our very own Milky Way, for example.

While we still don’t have a definitive answer on how these black holes take shape, one theory suggests that they form after the collapse of massive gas clouds when a new galaxy is coming into existence - thus explaining why these objects are found at the centres of galaxies.

Now astronomers have discovered what they suspect to be a ‘wandering’ black hole. Using NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton X-ray observatory, the researchers, led by Dacheng Lin from the University of New Hampshire, have observed a “hyper-luminous variable X-ray source” in the outskirts of the galaxy GJ1417+52 approximately 4.5 billion light years away.

“Its extreme brightness makes it likely that it is a black hole with a mass estimated to be about 100,000 times that of the sun,” states NASA.

Writing in The Astrophysical Journal (preprint), the authors explain this object could indeed be a rogue massive black hole. It is likely that it originally belonged to a smaller galaxy which collided with the bigger one, causing the hole to dislodge along with clouds of dust, stars, and gas.

The object was originally detected 16 years ago in July 2000, and between then and 2002 was found to be incredibly bright (although it has dimmed since then). The reason it’s emitting so many X-rays is likely because the black hole is destroying everything in its path as it shreds the edges of GJ1417+52.

Thankfully, the galaxy with its homeless massive black hole is far enough that we have nothing to worry about in our corner of the universe.

However, its detection not only advances our theoretical knowledge of such massive objects, but also serves as a reminder that some five billion years from now our own Milky Way is going to merge with the Andromeda galaxy. Black holes may get dislodged in that process, too. 

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