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The spacecraft spacecraft at NASA's Chandra X-ray observatory spotted a chain of black holes, neutron stars, or both in a huge ring-shaped collar surrounding the consequences of a galactic collision.
The ring of very bright X-ray sources surrounds galaxy AM 0644-741 which has collided with another galaxy (perhaps the one visible at the bottom left in the image above) in a past distant. The collision generated ripples that propagated in the AM 0644-741 gas (visible at the bottom right) and triggered the birth of new stars.
The most massive of these stars would have quickly exhausted their nuclear fuel and exploded in the form of supernovae, leaving in their wake black holes of stellar mass or compact neutron stars. Black holes of stellar masses generally have masses five to twenty times greater than those of the sun, while a neutron star, the collapsed nucleus of a sun six kilometers wide, has a mass of about 1, 5 times that of the sun. The sun
At least some of the black holes or neutron stars that revolve around 0644-741, some 300 million light-years away from Earth, are probably present in binary systems, sucking gas from their mates. This gas is heated to extreme temperatures as it is extracted, generating the high-energy X-rays detected by Chandra.
Interestingly, all X-ray sources circling AM 0644-741 are so bright that they are classified as ultra-bright X-ray sources, or ULX, producing hundreds or thousands of times the X-rays generated in a typical black hole or binary neutron star.
Astronomers initially thought that intermediate-mass black holes, with more than 100 times the mass of the Sun, were responsible for ULX. But this idea fell to the water when some ultra-bright X-ray sources in other galaxies, including the famous Whirlpool Galaxy M51, were found to include neutron stars.
It has been suggested that ULX could be the result of abnormally rapid growth of black holes or neutron stars or possibly the result of viewing geometry when the material is pulled along magnetic field lines. . As for AM 0644-741, astronomers do not yet know if X-ray sources reflect a mixture of black holes and neutron stars, or if they are all one or the other .
The Chandra study included observations of seven annular galaxies. Sixty-three X-ray light sources were detected, including 50 ULX. The observations are discussed in a paper written by team leader Anna Wolter of the INAF-Osservatorio Astronomico di Brera in Milan, Italy.
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