Things get messy in a pie-eating contest.
That’s because the competitors care about speed, not etiquette.
Astronomers used to think the same thing about black holes: The more they eat, the messier it gets.
But a new discovery has proved them wrong.
Researchers using the Gemini Observatory on Mauna Kea have found a small but surprisingly ravenous black hole in a distant galaxy.
And it has good table manners.
The unusual discovery, reported Thursday in the journal Nature, could force scientists to change their thinking about how some black holes consume matter.
The black hole is believed to be behind an energetic X-ray source called ULX-1 in the galaxy Messier 101, 22 million light-years away.
It’s a lightweight — only 20 to 30 times the mass of our sun. Yet it is consuming a huge amount of gas and dust stripped from a nearby star, all in orderly fashion.
"We thought that when small black holes were pushed to these limits, they would not be able to maintain such refined ways of consuming matter," research team member Stephen Justham, of the National Astronomical Observatories of China, said in a statement last week. "We expected them to display more complicated behavior when eating so quickly. Apparently we were wrong."
His team includes Ji-Feng Liu of Chinese Academy of Sciences, Paul Crowther of the University of Sheffield in England and Joel Bregman of the University of Michigan.
In order for the black hole to produce as much X-ray radiation as it does, it must be consuming matter close to the theoretical limits of consumption, the scientists concluded.
Small black holes typically give off high-energy or "hard" X-rays, while large black holes emit low-energy or "soft" X-rays.
But ULX-1 is dominated by soft X-rays, so researchers expected to find a larger black hole as its energy source.
"Theories have been suggested which allow such low-mass black holes to eat this quickly and shine this brightly in X-rays. But those mechanisms leave signatures in the emitted X-ray spectrum, which this system does not display," said Liu. "Somehow this black hole, with a mass only 20-30 times the mass of our sun, is able to eat at a rate near to its theoretical maximum while remaining relatively placid. It’s amazing."
The scientists had hoped to find an "intermediate mass" black hole — one with a mass between 100 and 1,000 times the mass of the sun. That would have put it between regular solar-mass black holes and the supermassive black holes that occupy the centers of galaxies, including the Milky Way.
"Many scientists thought it was just a matter of time until we had evidence for an intermediate-mass black hole in M101 ULX-1," said Liu.
But now it’s back to the drawing board,
To find the mass of the black hole, the researchers used the Multi-Object Spectrograph at the Gemini North telescope to measure the motion of the companion star, a variety known as Wolf-Rayet, which are hot and bright and lose mass rapidly due to a strong solar wind.
"Although this isn’t the first Wolf-Rayet black hole binary ever discovered, at some 22 million light-years away, it does set a new distance record for such a system," Crowther said. "The Wolf-Rayet star will have died in a small fraction of the time it has taken for light to reach us, so this system is now likely a double black hole binary."
