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Supermassive black holes found spiralling in at seven percent light speed
Quote:
Originally Posted by Ars Technica
Data from NASA’s Galaxy Evolution Explorer (GALEX) and the Hubble Space Telescope has confirmed the presence of a pair of supermassive black holes orbiting each other so closely that they're moving at relativistic speeds—a significant fraction of the speed of light.
Supermassive black holes are expected to come in pairs pretty often. That’s because every galaxy has its own supermassive black hole, and galaxies often merge, bringing the two together. These mergers are very slow processes that distort both galaxies until their stars settle into new orbits (a process known as "violent relaxation"). While this is happening, extremely heavy objects, such as supermassive black holes, will tend to move in toward the center of the new galaxy. The new galaxy would end up with two supermassive black holes, one from each original galaxy, orbiting each other at its core.
Objects have been observed which look a lot like supermassive black hole binaries, matching the prediction. These objects have a lot of mass—billions of times the mass of the Sun, as we’d expect from a pair of supermassives—and they’re periodic, meaning the amount of light the object produces rises and falls with a predictable time period.
(It may at first seem contradictory to think of light coming from a black hole, an object from which no light can escape. The light doesn’t actually come from the black hole itself but from matter falling in, which produces light from the incredible friction it experiences as it speeds up, spiraling into the black hole).
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To confirm it was a black hole pair exhibiting relativistic beaming, the researchers needed data on the patterns of light extending over many years. That’s because the pair take about five years to complete one orbit, making it tricky to get the full pattern. Luckily, GALEX and Hubble both had data going back 20 years in different wavelengths, providing a treasure trove.
"We were lucky to have GALEX data to look through," said co-author David Schiminovich of Columbia University in New York. "We went back into the GALEX archives and found that the object just happened to have been observed six times."
Both telescopes captured data in the ultraviolet portion of the spectrum, which showed the sudden brightening and darkening due to relativistic beaming. "It's as if a 60-Watt light bulb suddenly appears to be 100 Watts," said D'Orazio. "As the black hole light speeds away from us, it appears as a dimmer 20-Watt bulb."
The use of ultraviolet in particular was important because it helped confirm the researchers’ prediction. “We have predicted that UV light should have a larger amplitude of variability than the light in the optical part of the electromagnetic spectrum, and this is what we find in the data,” D’Orazio told Ars. In other words, the brightness varies more in UV than in visible light, confirming predictions for a binary black hole system with relativistic beaming. “The point being that relativistic beaming gives a good case for what we are seeing in PG 1302, and it looks like what we see is caused by BHs orbiting very close to each other very fast.”
Supermassive black holes are expected to come in pairs pretty often. That’s because every galaxy has its own supermassive black hole, and galaxies often merge, bringing the two together. These mergers are very slow processes that distort both galaxies until their stars settle into new orbits (a process known as "violent relaxation"). While this is happening, extremely heavy objects, such as supermassive black holes, will tend to move in toward the center of the new galaxy. The new galaxy would end up with two supermassive black holes, one from each original galaxy, orbiting each other at its core.
Objects have been observed which look a lot like supermassive black hole binaries, matching the prediction. These objects have a lot of mass—billions of times the mass of the Sun, as we’d expect from a pair of supermassives—and they’re periodic, meaning the amount of light the object produces rises and falls with a predictable time period.
(It may at first seem contradictory to think of light coming from a black hole, an object from which no light can escape. The light doesn’t actually come from the black hole itself but from matter falling in, which produces light from the incredible friction it experiences as it speeds up, spiraling into the black hole).
...
To confirm it was a black hole pair exhibiting relativistic beaming, the researchers needed data on the patterns of light extending over many years. That’s because the pair take about five years to complete one orbit, making it tricky to get the full pattern. Luckily, GALEX and Hubble both had data going back 20 years in different wavelengths, providing a treasure trove.
"We were lucky to have GALEX data to look through," said co-author David Schiminovich of Columbia University in New York. "We went back into the GALEX archives and found that the object just happened to have been observed six times."
Both telescopes captured data in the ultraviolet portion of the spectrum, which showed the sudden brightening and darkening due to relativistic beaming. "It's as if a 60-Watt light bulb suddenly appears to be 100 Watts," said D'Orazio. "As the black hole light speeds away from us, it appears as a dimmer 20-Watt bulb."
The use of ultraviolet in particular was important because it helped confirm the researchers’ prediction. “We have predicted that UV light should have a larger amplitude of variability than the light in the optical part of the electromagnetic spectrum, and this is what we find in the data,” D’Orazio told Ars. In other words, the brightness varies more in UV than in visible light, confirming predictions for a binary black hole system with relativistic beaming. “The point being that relativistic beaming gives a good case for what we are seeing in PG 1302, and it looks like what we see is caused by BHs orbiting very close to each other very fast.”
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