So quickly records fall. Just two weeks after finding what was then the biggest stellar-formed black hole ever observed, astronomers have found another one that's even bigger. Way bigger.
Stellar black holes differ in several ways from their gargantuan cousins in the center of galaxies. Most noticeably, they're orders of magnitude smaller, formed from the collapse of a single large star.
Like the one found previously, this week's new record holder exists in a stellar pair, being circled by a hot star. Gas is being ejected from the star and is sucked into the black hole, giving off X-rays that help astronomers understand the system's interaction.
The previous find, a black hole nearly 16 times the mass of our sun, had already stretched astronomers' understanding of how such objects might form. Now this one turns up at somewhere between 24 times and 33 times solar mass.
Astronomers had previously believed that black holes of this size wouldn't be found above about 15 times solar mass, because the huge stars that create them blow off large quantities of gas before reaching the stage of explosion and collapse.
Researchers now theorize that the current black hole, located in a dwarf galaxy about 1.8 million light years from earth, must have been about 60 times the mass of the sun before exploding. With a low proportion of heavy elements such as carbon and oxygen, which are more susceptible to being "blown" away in the gas-shedding process, they say it could have retained more of its mass before the end of its life.
By contrast, the heavy element-rich stars in our own galaxy would be unlikely to form such large black holes, the researchers say.
A paper on the discovery will be published in the November 1 issue of Astrophysical Journal Letters.
Massive Black Hole Smashes Record [Harvard-Smithsonian press release]
(Image: Artist's conception of companion star's gas spiraling into black hole. Credit: Aurore Simonnet/Sonoma State University/NASA)
