Space

Slow-dancing supermassive black holes are orbiting at a snail's pace

Slow-dancing supermassive blac...
Astronomers have observed a pair of supermassive black holes orbiting each other in a distant galaxy
Astronomers have observed a pair of supermassive black holes orbiting each other in a distant galaxy
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Astronomers have observed a pair of supermassive black holes orbiting each other in a distant galaxy
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Astronomers have observed a pair of supermassive black holes orbiting each other in a distant galaxy

Supermassive black holes lie at the center of most galaxies, but 750 million light-years away, a huge galaxy known as 0402+379 boasts two of them – and one appears to be orbiting the other. The discovery is the result of 12 years of observation, and while it's long been suspected, this marks the first time the phenomenon has been directly seen.

Massive and elliptical, 0402+379 is an unusual galaxy. In 2006 it was discovered to be home to a supermassive black hole binary, and it's been under observation by radio telescopes in the Very Long Baseline Array (VLBA) ever since. Between them, the black holes share a mass of about 15 billion times that of the Sun, ranking them among the largest ever found, and with just seven parsecs separating them, they're also the closest known pair.

Twelve years of VLBA observations have shown astronomers that one of the black holes is orbiting the other, albeit extremely slowly. The team calculated that a single orbit may take the black hole some 24,000 to 30,000 years to complete, which makes its motion very difficult to detect.

"If you imagine a snail on the recently discovered Earth-like planet orbiting Proxima Centauri – a bit over four light years away – moving at one centimeter a second, that's the angular motion we're resolving here," says Roger W. Romani, co-author of the paper.

These black hole binaries are thought to be caused by cosmic collisions between galaxies. Long ago, 0402+379 may have gotten its bloated shape and double-black-hole-center from merging galaxies, and it could teach scientists a lot about the lifespan of galaxies – especially since the same fate awaits the Milky Way, with the Andromeda galaxy speeding towards us right now.

"For a long time, we've been looking into space to try and find a pair of these supermassive black holes orbiting as a result of two galaxies merging," says Greg Taylor, lead researcher on the study. "Even though we've theorized that this should be happening, nobody had ever seen it until now."

Ultimately, the black holes involved in these mergers are expected to blend together as well, creating gravitational waves. Early last year, LIGO detected these ripples in space-time caused by merging black holes, but those two only had a mass of about 30 times the Sun. If 0402+379 ever collide, the resulting gravitational radiation burst would be larger by a factor of a billion.

But that's a pretty big "if", according to the researchers. Given the extremely slow orbit, the universe will probably end before the two black holes ever become one – making them the most tantalizing "will they?/won't they?" couple in the universe we know of.

The research was published in The Astrophysical Journal.

Sources: University of New Mexico, Stanford University

4 comments
lab220
The angular motion may be slow, but the actual speed is very fast and easy to calculate. For simplicity's sake, I will assume a circular orbit. In that case, the speed = distance / time = (pi * 7 parsecs) / (30,000 * 365 * 24 * 60 * 60 seconds). Replacing 7 parsecs by 2.16e+17 metres, you get a speed of around 700 km/s (2.5 million kph or 1.6 million mph).
piperTom
Thanks to lab220 for the conversion, but it does not change the fact that these two take a looooong time to complete one orbit. Which raises another question: how did these two get so close together? It's just 22 light years; nothing on a galactic scale. And they had much less than 13 billion years to settle down. The next project for these astronomers is to do modeling to see how two galaxies could collide and then lose angular momentum so as to be nearly at rest in the limited time we have.
Reid Barnes
Why do they cling to a gravitational model of cosmology based on the general theory of relativity? Has the general relativity road of twentieth century cosmology become a new religion masquerading as science? Few religions have been as persistent as this one. It has distorted scientific inquiry for over a century now. Not only have there been decades of fruitlessly funded efforts to find “dark matter,” but everything from black holes to dark energy to the accelerating universe is theorized using this gravitational model. Have we really changed when it comes to science establishments? Think back to the arrest of Galileo or back to Ptolemy and the epicycles. The model they cling to is based on the general theory of relativity, and the theory has led to the conclusion that the outer reaches of the universe are not only expanding at an accelerating rate but have reached an expansion rate faster than the speed of light. Well, the general theory of relativity, it turns out, is based on self-contradicting non-Euclidean geometry. Here is a link to an explanation about the self-contradicting non-Euclidean geometry and why because of it general relativity lost its coordinate system. Part II of the article explains why this flaw was overlooked throughout the twentieth century. You can understand it even if your math education didn't exceed high school geometry. The link is in the brackets: [https://www.facebook.com/notes/reid-barnes/when-is-an-assertion-about-coordinates-merely-an-assertionan-unsupported-asserti/789731027746140]
Ichabod Ebenezer
Perhaps I'm not used to thinking big enough, but 7 parsecs, or 22 light years sounds pretty far to me. Just to bring it down to numbers the average person can grasp, you can fit 73,000 of our solar systems, out to the furthest orbit of Pluto, between those two black holes with room to spare.