in the Large Magellanic Cloud, a companion galaxy to the Milky Way; in the constellation Dorado
5 to 13 times the mass of the Sun
Diameter roughly equal to the size of a city
Located in the Large Magellanic Cloud, a small companion galaxy to the Milky Way, LMC X-3 is a binary system that consists of a black hole and a "normal" star that is much hotter, bigger, and more massive than the Sun.
The system was discovered by an orbiting X-ray telescope in 1971. In the four decades since, several teams of astronomers have studied the system with optical telescopes on the ground and ultraviolet and X-ray telescopes in orbit.
The two stars orbit each other every 1.7 days, at a distance of seven million miles (11 million km). The companion star is spectral class B5, which means its surface is thousands of degrees hotter than the surface of the Sun. The star is 5.9 times the mass of the Sun.
The black hole's gravity pulls hot gas from the companion's outer layers, forming an accretion disk. This disk is so hot that it heats the side of the star that faces the black hole, making that hemisphere several thousand degrees hotter than the other.
Based on the motions of the two stars, the spectral type of the bright companion, and other factors, different teams have determined different masses for the black hole, from roughly 5 to 13 times the mass of the Sun.
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This document was last modified: December 29, 2010.