Galaxy by thrusting neighbor to spawn giant ring of black holes

A composite image of the ring galaxy AM 0644-741. The image contains X-ray data from the Chandra X-ray Observatory (purple) and optical data from NASA’s Hubble Space Telescope (red, green, and blue). The galaxy AM 0644 is located in the lower right corner.

(NASA/CXC/INAF/A. Wolter et al; NASA/STScI)

A giant ring of black holes discovered 300 million light-years away, providing new clues about what happens when galaxies collide.

With the help of NASA’s Chandra X-ray Observatory, astronomers detected a very bright source of x-ray radiation that is likely to be stirred up by a ring of stellar mass black holes or neutron stars — the small, dense bodies left after a stellar explosion, according to a new study.

The bright X-ray source comes from the ring galaxy AM 0644-741 (abbreviated’M 0644), which is located about 300 million light-years from Earth. By combining data from Chandra and NASA’s Hubble Space Telescope, astronomers created a composite image of X-ray and optical observations of the milky way. [Images: Black Holes of the Universe]

The observed ring of black holes or neutron stars is believed to be the result of a galaxy collision. The galaxies are probably brought together by the force of gravity and the gravitational pull of a galaxy made waves in the gas surrounding its neighbor, which in this case is AM 0644. The ripples would cause the gas to expand or to group together, in denser areas, triggering the birth of new stars.

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  • Images: Black Holes of the Universe

  • X-ray sources

“The most massive of these young stars will lead short lives in cosmic terms of millions of years,” representatives of the Chandra X-ray Observatory said in a statement. “After their nuclear fuel is spent, and the stars explode as supernovae, leaving behind the two black holes with masses typically between five to twenty times that of the sun, or neutron stars with a mass approximately equal to that of the sun.”

The black holes or neutron stars have a close cosmic companions from which they siphon gas. This gas falls inward and is heated by friction, causing the bright X-rays detected by Chandra, according to the statement.

What’s more, the bright X-rays of AM 0644 are classified as ultraluminous X-ray sources (ULXs). These objects produce hundreds to thousands of times more X-rays than most other neutron star or black hole X-ray binaries. However, the identity of the individual ULXs in AM 0644 is currently unknown, according to the statement.

In addition to the ring of black holes or neutron stars surrounding’M 0644, the Chandra data revealed that a supermassive black hole at the center of the milky way, as well as a rapidly growing black hole that is located behind the galaxy at a distance of 9.1 billion light-years from Earth.

And I’M 0644 wasn’t the only ring galaxy Chandra inspected. The telescope observed six other ring galaxies, revealing a total of 63 X-ray sources, 50 of which are considered ULXs.

In fact, the seven-ring galaxies contain a higher number of ULXs per galaxy than other types of galaxies. Therefore, these galaxies can help astronomers better understand the origin of ULXs, according to the statement.

The study was published Aug. 10 in The Astrophysical Journal and is available online.

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