Black holes have always been fascinating subject to me. You can find more about black holes in Big Bang series here. If you remember from that article, or from whatever source you heard of it, there has been some established rule in size/mass of black hole and hosting galaxy black hole size/mass. To the best of our astronomical knowledge, almost every galaxy should contain in its central region what is called a supermassive black hole: a black hole with a mass between that of hundreds of thousands and billions of Suns. The best-studied super-massive black hole sits in the center of our home galaxy, the Milky Way, with a mass of about four million Suns. For the masses of galaxies and their central black holes, an intriguing trend has emerged: a direct relationship between the mass of a galaxy's black hole and that of the galaxy's stars. Typically, the black hole mass is a tiny fraction of the galaxy's total mass. A few years ago, astronomers discovered that there appears to be a relationship between the mass of the galaxy’s central black hole and the mass of the galaxy’s inner region, called the bulge. A bigger bulge means a bigger black hole. That ratio is interesting: In general, it holds true across a wide range of galaxies. For some reason, properties of the central black hole and the greater galaxy around it are tied together. That’s telling us something about how galaxies form and how they grow, if we can just figure out why they’re connected. But things are about to get mroe complicated.
Search led by Remco van den Bosch has discovered a massive black hole that could upset the accepted relationship between black hole mass and galaxy mass, which plays a key role in all current theories of galaxy evolution. With a mass 17 billion times that of the Sun, the newly discovered black hole in the center of the disk galaxy NGC 1277 might even be the biggest known black hole of all: the mass of the current record holder is estimated to lie between 6 and 37 billion solar masses; if the true value lies towards the lower end of that range, NGC 1277 breaks the record. At the least, NGC 1277 harbors the second-biggest known black hole.
The big surprise is that the black hole mass for NGC 1277 amounts to 14% of the total galaxy mass, instead of usual values around 0,1%. This beats the old record by more than a factor 10. Astronomers would have expected a black hole of this size inside blob-like ("elliptical") galaxies ten times larger. Instead, this black hole sits inside a fairly small disk galaxy. Is this surprisingly massive black hole a freak accident? Preliminary analysis of additional data suggests otherwise - so far, the search has uncovered five additional galaxies that are comparatively small, yet, going by first estimates, seemed to harbor unusually large black holes too. More definite conclusions have to await detailed images of these galaxies. If the additional candidates are confirmed, and there are indeed more black holes like this, astronomers will need to rethink fundamentally their models of galaxy evolution. In particular, they will need to look at the early universe: The galaxy hosting the new black hole appears to have formed more than 8 billion years ago, and does not appear to have changed much since then. Whatever created this giant black hole must have happened a loooong time ago.
With all the talk about black holes reopened now, with discussions going on about firewall topic and others, we may end up calling black holes - dark holes. Speaking of which, and somewhat unrelated, a remarkable observation by astronomers from the University of Southampton has appeared in The Astrophysical Journal. They revealed that bright X-ray flares in nearby galaxies, once assumed to indicate the presence of black holes, can in fact be produced by white dwarfs. White dwarfs are very common, burnt-out cinders of normal stars like the Sun that are typically about one solar mass but are contained in a volume no bigger than Earth.
Credits: Max Planck Institute for Astronomy