We tend to think of supermassive black holes as relatively stationary things, sitting there in the center of a galaxy while everything else swirls around it.
But this is not always the case, and now astronomers have the best evidence of a supermassive black hole that not only moves through the Universe, but moves within its own galaxy. He has ants in his pants and witches in his witches, and while it’s not clear why, the possible explanations are really exciting.
“We don’t expect most supermassive black holes to move; they usually settle for sitting,” said astronomer Dominic Pesce of the Harvard & Smithsonian Center for Astrophysics.
“They’re so heavy that it’s hard to get them up and running. Think about how much harder it is to throw a moving bowling ball than to make a soccer ball, realizing that in this case the” ball of bowling “is several million times the mass of our Sun. This will require a fairly powerful kick.”
It is not easy to make a peripatetic supermassive black hole. They can only be found across immense gulfs of space, millions to billions of light-years away; at these distances, isolating the motion of an object – even if that object is a supermassive black hole – across an entire galaxy is a challenge.
Pesce and his team thought they might get a little lucky with a type of galactic core called a megamaser. It is a type of supermassive black hole active with a gas and dust accretion disk that is included on it, generating large amounts of heat and light.
With a megamaser, there is an additional ingredient to this formula: molecules such as hydroxyl, water, formaldehyde, and methine that amplify the luminosity of the nucleus at microwave wavelengths.
Using a technique called very long baseline interferometry, which combines the observations of a network of radio telescope antennas to effectively create a huge observation plate, the speeds of these megamassers can be measured very accurately.
In studying water megamassers in particular, Pesce and colleagues hoped to be able to identify any supermassive black hole that moved at a different speed in the galaxy around them.
“We asked: Are the speeds of black holes the same as those of the galaxies in which they reside?” He said. “We hope they have the same speed. If they don’t, that means the black hole has been drilled.”
The team looked closely at 10 megamassers, comparing black hole speed data with observations from across the galaxy. Indeed, nine of them were consistent with our expectations of supermassive black holes hiding in the galactic center, like a spider in the web.
One of them, however, showed a different behavior. The spiral galaxy J0437 + 2456, located about 228 million light-years away, has a supermassive black hole about 3 million times the mass of the Sun, which appeared to be moving at a speed significantly different from the rest of the galaxy.
According to the team’s analysis, the speed of the supermassive black hole is about 4,810 kilometers per second (2,990 miles per second). The galaxy’s neutral hydrogen, on the other hand, appears to be receding at a speed of 4,910 kilometers per second. According to observations of star and gas motions, the speed of the inner region of the galaxy is 4,860 kilometers per second.
Because all of these measurements differ significantly from each other and the entire structure of the galaxy’s speed seems quite complicated, it’s hard to know exactly why everything is faltering.
There are several possible explanations. The galaxy could be experiencing a continuous encounter with another massive object, such as another galaxy. The supermassive black hole could have collided with another supermassive black hole, generating a setback that pushed the black hole out of position; hesitation could be the galaxy and the black hole receding.
Or the black hole could have an invisible binary companion, the two objects orbiting a center of mutual gravity within the galactic nucleus.
“Despite all the expectations that they really should be out there with some abundance, scientists have had a hard time identifying clear examples of supermassive black binary holes,” Pesce said.
“What we might see in the galaxy J0437 + 2456 is one of this pair’s black holes, and the other is hidden in our radio observations due to its lack of maser emission.”
Whether it’s a setback or a binary companion, this would be extraordinary news for astrophysics. There are many unanswered questions about supermassive black holes, such as how they become so large and whether supermassive black hole binaries can close the final parsec away from each other. The evidence of supermassive black hole binaries and fusions could help us answer these questions.
It is also great news for us in the Milky Way: since we are a few million years away from a galactic fusion, there is very little chance that our supermassive black hole, Sagittarius A *, will develop greed any time soon.
The team hopes to make more observations about the galaxy and its peculiar core to try to reduce the cause of its strange behavior.
The research has been published in The Astrophysical Journal.