Two of the knots, they concluded, had been in all probability small galaxies with small inner motions being cannibalized by the large galaxy. Measurements of the third knot had such massive error bars that it couldn’t but be dominated in or out because the black gap’s location.
The fourth, very compact knot close to the underside fringe of the core was too faint even for the Hubble, Dr. Burke-Spoloar reported. “Observing this knot would have required an overblown period of time (tons of of hours) observing with Hubble Area Telescope,” she mentioned in an e mail, and so it additionally stays a candidate for the black-hole hiding spot.
The galaxy core additionally emits radio waves, however they didn’t assist the search, Dr. Burke-Spolaor mentioned.
“We had been initially hoping the radio emission can be some form of literal smoking gun, displaying an lively jet that factors straight again to black-hole location,” she mentioned. However the radio relic was at the very least 50 million years previous, in accordance with its spectral traits, which meant, she mentioned, that the massive black gap would have had ample time to maneuver elsewhere for the reason that jet turned off.
Subsequent cease was NASA’s orbiting Chandra X-ray Observatory. Kayhan Gultekin of the College of Michigan, one other veteran Nuker who was not on the unique discovery crew, aimed the telescope on the cluster core and people suspicious knots. No cube. The putative black gap must be feeding at one-millionth of its potential price if it had been there in any respect, Dr. Gultekin mentioned.
“Both any black gap on the middle could be very faint, or it isn’t there,” he wrote in an e mail. The identical goes for the case of a binary black-hole system, he mentioned; it could have to be consuming little or no gasoline to remain hidden.
Within the meantime, Imran Nasim, of the College of Surrey within the U.Ok., who was not a part of Dr. Postman’s crew, has revealed a detailed analysis of how the merger of two supermassive black holes may reform the galaxy into what the astronomers have discovered.
“Merely, gravitational wave recoil ‘kicks’ the supermassive black gap out of the galaxy,” Dr. Nasim defined in an e mail. Having misplaced its supermassive anchor, the cloud of stars across the black gap binary spreads out, turning into extra diffuse. The density of stars in that area — the densest a part of your entire large galaxy — is simply one-tenth the density of stars in our personal neighborhood of the Milky Manner, leading to an evening sky that would seem anemic in contrast with our personal.