Archive for the ‘Astrophysics and cosmology’ Category

Intermediate mass black holes

July 4, 2009

Black holes are controversial. (Just browse reader comments from partisans of various sorts of “alternative” astrophysical theories – which can be found at the end of many articles dealing with black holes that allow commenting by the general public.)

Nevertheless, very solid evidence has been accumulated over the years for the existence of two types of black holes: stellar-mass black holes with masses from 3 to several tens of solar masses (M), and supermassive black holes, which are vastly larger – generally millions to billions M. Concerning some of the evidence, see here.

Stellar-mass black holes are easy to explain as supernova remnants, while supermassive black holes seem to be an inseparable concomitant of the development of all galaxies.

Perhaps surprisingly, however, there has been very little evidence for the existence of black holes of intermediate mass. If such black holes exist at all, the processes that form them must be rather more unusual. Evidence for the existence of intermediate mass black holes has been reported in the past. (There’s some discussion here of possible black holes of mass less than a million M.)

But because black holes, by their nature, are difficult to observe directly, and so their existence must be inferred indirectly, it has been difficult to come up with relatively unambiguous evidence. Now we have announcements of better evidence in two cases.