Hunger Pangs in Supermassive Black Holes

[Recusant]

The title of this thread is silly clickbait, but the topic is interesting from an astronomy and/or cosmology point of view. For some time there has been a mystery regarding the supermassive black holes found at the centers of galaxies. Observations seem to show two classes of black holes--more or less regular ones (stellar black holes) equivalent of up to multiple tens of solar masses, and the immense ones mentioned above, which tend to be orders of magnitude larger; several hundreds of thousands to billions of solar masses. Despite a hypothetical intermediate range of black holes between these two classes, none have ever been observed.

Moreover, it appears that the Universe isn't old enough to allow enough time for a stellar black hole to grow to a supermassive black hole. Still, the observations that indicate their existence seem unequivocal. So how did they form?

While not a complete solution to this mystery, the story below gives some hope that scientists will gain a better understanding of supermassive black holes. Of course it presents its own mystery. 

"New way supermassive black holes are 'fed'" | ScienceDaily

Supermassive black holes weigh millions to billions times more than our sun and lie at the center of most galaxies. A supermassive black hole several million times the mass of the sun is situated in the heart of our very own Milky Way.

Despite how commonplace supermassive black holes are, it remains unclear how they grow to such enormous proportions. Some black holes constantly swallow gas in their surroundings, some suddenly swallow whole stars. But neither theory independently explains how supermassive black holes can "switch on" so unexpectedly and keep growing so fast for a long period.

A new Tel Aviv University-led study published today in Nature Astronomy finds that some supermassive black holes are triggered to grow, suddenly devouring a large amount of gas in their surroundings.

In February 2017, the All Sky Automated Survey for Supernovae discovered an event known as AT 2017bgt. This event was initially believed to be a "star swallowing" event, or a "tidal disruption" event, because the radiation emitted around the black hole grew more than 50 times brighter than what had been observed in 2004.

However, after extensive observations using a multitude of telescopes, a team of researchers led by Dr. Benny Trakhtenbrot and Dr. Iair Arcavi, both of TAU's Raymond & Beverly Sackler School of Physics and Astronomy, concluded that AT 2017bgt represented a new way of "feeding" black holes.

[. . .]

"We are not yet sure about the cause of this dramatic and sudden enhancement in the black holes' feeding rate," concludes Dr. Trakhtenbrot. "There are many known ways to speed up the growth of giant black holes, but they typically happen during much longer timescales."

"We hope to detect many more such events, and to follow them with several telescopes working in tandem," says Dr. Arcavi. "This is the only way to complete our picture of black hole growth, to understand what speeds it up, and perhaps finally solve the mystery of how these giant monsters form."

[Link to full story]

[xSilverPhinx]

Black holes are fascinating.