Astronomers spot the very first intermediate-mass black hole (stars, light, solar)

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Astronomers spot the very first intermediate-mass black hole

An international team of astronomers have uncovered the first reported mid-sized black hole through Australia’s CSIRO radio telescope. Dubbed Hyper-Luminous X-ray Source 1 (or HLX-1 for short), the black hole was spotted in ESO 243-29, a galaxy 300 million light-years away. The chance discovery occurred when researchers noticed the black hole emitting vast amounts of X-rays.

Prior to this only “stellar mass” and supermassive black holes were observed, the latter possessing mass up to a billion times that of the Sun. Dr. Sean Farrel, ARC Postdoctoral Fellow at the University of Sydney, estimates the likely mass of the black hole to be around 20,000 solar masses, although researchers have placed an upper limit of up to 90,000 solar masses.

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“We don’t know for sure how supermassive black holes form, but they might come from medium-size ones merging. So finding evidence of these intermediate-mass black holes is exciting.”

Source: Astronomers spot the very first intermediate-mass black hole | The Bunsen Burner

Mergers would seem to be the most likely way super massive black holes are formed. If we exclude the possibility of primordial black holes, then the only possible way a black hole could form is through the death of a star of at least 10 solar masses.

In the early universe, some 30 million years after the Big Bang, the first stars formed. These Population III (made from hydrogen and helium only, no metals) stars were much more massive than the Population II and I stars we see in our universe today. Some estimate Population III stars could have been 1,000 solar masses or more.

In an interesting twist, stars that have between 130 and 250 solar masses do not produce black holes when they die. According to recent observations, stars with 130 to 250 solar masses die in what has been called a "pair-instability supernova" which leaves nothing behind. However, stars more massive than 250 solar masses (which are extremely rare these days) do produce black holes when they die.

While we have not yet observed black holes merging, we have observed galactic collisions involving two or more galaxies with super massive black holes. This, however, is the first dwarf galaxy were we have discovered a super massive black hole well under a million solar masses. It is also colliding with another galaxy, which is why this intermediate sized black hole is emitting x-rays. Most super massive black holes, including our own in the Milky Way, are not "bulking up" on other material. They are relatively quiet, which makes them incredibly difficult to detect.

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