Alternate Names

Sagittarius A*

Type

Supermassive

Location

In the constellation Sagittarius

Finder Chart

Distance

27,000 light-years (8 kiloparsecs)

Mass

4.1 million times the mass of the Sun

Size

Diameter roughly 15 million miles (24 million km).

Discovery Methods

• Measuring the motions of stars

Measuring the motions of stars

Because a black hole is both massive and compact, it exerts a strong gravitational pull on the material around it. Astronomers can deduce the presence of a supermassive black hole in the core of a galaxy by measuring the velocities of stars that orbit the black hole. A more-massive black hole will accelerate nearby stars to greater speeds, so the velocities of stars can reveal not only the presence of a black hole, but its mass as well.

More about black hole discovery methods »

This document was last modified: February 12, 2012.