Type

Stellar mass

Location

In M33, the Triangulum galaxy

Finder Chart

Distance

2.7 million light-years (0.84 megaparsecs)

Mass

About 15.7 times the mass of the Sun

Size

Diameter roughly 60 miles (95 km)

Discovery Methods

• Detection of an accretion disk
• Measuring the motions of a companion star

Detection of an accretion disk

Although a black hole itself is invisible to the outside universe, many black-hole systems produce copious amounts of X-rays or ultraviolet radiation. That is because disks of superhot gas encircle the black holes. In the case of a star-sized black hole, the gas usually comes from a nearby companion star; the black hole's powerful gravity pulls gas off the surface of the star. In the case of a supermassive black hole, the gas comes from large clouds of gas in the crowded core of a galaxy, or from stars that pass close to the black hole and are torn apart by its gravitational pull. As the gas spirals into the black hole, it forms a wide, flat "accretion disk." The gas moves faster and faster as it spirals closer, so it's heated to millions of degrees. At such temperatures, the gas radiates most strongly in ultraviolet or X-ray wavelengths. These wavelengths are blocked by Earth's atmosphere, so only telescopes in space can detect them.

More about black hole discovery methods »

This document was last modified: January 24, 2011.