Black hole’s annual feast begins
by Nadia Drake
HLX-1, the only known intermediate-mass black hole (circled), hovers above the plane of a nearby galaxy, as seen in this Hubble Space Telescope image. Astronomers are debating the source of the light coming from the area around the black hole.NASA, ESA, S. Farrell/Sydney Institute for Astronomy
BEIJING — A black hole about 290 million light-years away has just begun slurping material from its surroundings, an annual ritual revealed by a periodic brightening in X-ray wavelengths.
“It is picking up again, just today — or last night — which is good,” astronomer Roberto Soria of the International Center for Radio Astronomy Research in Perth, Australia, said August 22 at the 28th General Assembly of the International Astronomical Union. “I was starting to get a bit worried because this cycle was three or four days late.”
The black hole, known as HLX-1, is 10,000 times as massive as the sun and the only known specimen in its weight class. Middleweights like HLX-1, which should be numerous, are intermediate between the supermassive black holes at galactic cores — as massive as billions of suns — and the featherweights with just a few solar masses.
First detected by X-ray telescopes in 2009, HLX-1 has since been spied upon in visible wavelengths by the Hubble Space Telescope and other instruments. Those observations revealed a mysterious, bluish glow surrounding the object, which hovers above the plane of a distant galaxy. Now, scientists are trying to determine where the glow is coming from, how HLX-1 formed, and where the rest of the intermediate-mass black holes are hiding.
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