Contact StarDate | About StarDate | Friends of McDonald | Sign up for SkyTips

Milky Way Sagittarius A*

Printable version

Home > Directory > Supermassive

Type

Supermassive

Location

In the constellation Sagittarius

Finder Chart

Distance

27,000 light-years (0.008 megaparsecs)

Mass

2.6 million to 4 million times the mass of the Sun

Size

Diameter roughly 10 million-15 million miles (16-24 million km).

Discovery Methods

Measuring the motions of stars

Milky Way Sagittarius A*

The center of the Milky Way galaxy is a turbulent, dynamic region of bright star clusters, clouds of hot gas, and monstrous magnetic fields. And they all seem to center on a small, dense object known as Sagittarius A* (Sgr A*). Observations of stars orbiting this point suggest that it is a supermassive black hole. There is little gas spiraling into Sagittarius A*, perhaps because exploding stars have blown away much of the gas and dust from the Milky Way's core.

Although this is by far the closest supermassive black hole, it is still relatively difficult to study because it lies behind many thick clouds of interstellar dust, which absorb visible light. Astronomers rely on X-rays, radio waves, and other wavelengths of energy to study the Milky Way's core.

News

Whirling Around the Milky Way (ESO News)
European astronomers have monitored the orbits of about 30 stars in the center of the Milky Way galaxy to learn more about the galaxy's central black hole and the environment around it.

Astronomers Find Suspected Medium-Sized Black Hole in Omega Centauri (McDonald Observatory News)
A well-known star cluster that glitters with the light of millions of stars may have a mysterious dark object tugging at its core, according to researchers at The University of Texas at Austin.

Astronomers Get Closest Look Yet At Milky Way's Mysterious Core (National Radio Astronomy Observatory)
Using a planet-wide array of radio telescopes, astronomers have come closer than ever before to measuring the size of the suspected black hole at the center of the Milky Way. They determined that a source of radio waves in the galaxy's core is no larger than the distance between Earth and the Sun (less than 100 million miles/150 million km). The radio waves probably come from a ring of material that encircles the black hole.

Milky Way's Quiet Black Hole Flared in Past (StarDate)
Oliver Cromwell had Charles I beheaded, toppling the British monarchy. An outbreak of plague shut down Cambridge University, leaving 22-year-old student Isaac Newton to return home and spend his leisure hours creating, among other things, the theory of gravity. And had they existed then, space-borne gamma-ray telescopes would have seen the black hole at the center of our Milky Way galaxy flare to life.

Scientists look into Milky Way core (BBC News)
A team of astronomers led by Andrea Ghez at the University of California at Los Angeles has pinpointed the location of Sagittarius A* with the greatest accuracy to date by observing three stars that orbit the object.

Ghez and colleagues collected infrared images of the Milky Way's core over a four-year period using the 10-meter Keck telescope in Hawaii. The positions of the stars nearest Sagittarius A* change significantly in only a few years, implying that they orbit a compact, massive body at the position of Sagittarius A*.

A Daring Journey

Birth of Supermassive Black Holes: Battle in the Bulge

Galactic Monsters