Supermassive Black Holes

Rob Thacker
20 January 2012

Just last week, researchers announced the discovery of the two most massive black holes ever found: one 21 billion times the mass of our Sun, and another 9.7 billion times the mass of the Sun. These two black holes were found in the middle of two huge galaxies called NGC 3842 and NGC 4889. Each of these galaxies is around 10 times more massive than our own galaxy, the Milky Way. Black holes are regions in space resulting from stars that have "died" and collapsed in on themselves. Their gravitational field is so strong that nothing can escape, not even light.

Did You Know?
Black holes don't suck things in. If we turned the Sun into a black hole tomorrow, the Earth would continue orbiting around just as it has for billions of years.

We've known about the existence of “supermassive” black holes for quite some time, our own galaxy even has one. The black hole in the middle of the Milky Way is called Sagittarius A and it has a mass of around 4 million Suns. But compared to the newly discovered black holes it's a thousand times smaller. That's what makes this new discovery so surprising: the two new black holes are bigger than anyone anticipated!

Did You Know?
Black holes actually end up releasing a lot of energy into the environment around them. Material gets very hot when it falls into a black hole and can drive “winds” of gas between stars at many thousands of kilometers per second.

Over the past 15 years or so, astrophysicists developed a theory to estimate the mass of a black hole relative to the galaxy it resides in. Most of the observed black hole masses and galaxy masses seemed to fit this relationship quite well. However, with the new black holes being more massive than expected, it looks like astrophysicists need to revise the theory for how black holes grow inside giant elliptical galaxies like NGC3842 and NGC4889. This is actually very exciting as it means that there could be physical processes involved in the growth of black holes that we still don't know much about.

Did You Know?
Some theories of space and time suggest black holes may contain gateways to other Universes within them.

But before astrophysicists start revising their models, we really need more observations. At present, with only two of these huge black holes, there is not much data to go on. Could these two black holes be special cases? It's possible! However, astronomers have just about reached the limit of what we can measure in the nearby universe, our telescopes just aren't big enough to go farther. So to see more massive black holes within galaxies we need an entirely new generation of telescopes like the Thirty Meter Telescope, or European Extremely Large Telescope.

Learn more!

Guardian: Supermassive Black Holes

Article first published January 10, 2012

Rob Thacker

I am a Professor of astronomy at Saint Mary's University in Halifax, Nova Scotia. I use supercomputers to answer questions about how galaxies form and evolve. As well as being interested in things in the sky, I am also passionate about our planet and take time to go backpacking or diving with my wife Linda whenever possible. English by birth, I still haven't quite gotten used to Canadian winters!


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