Discovery of Sagittarius A*

The center of the Milky Way is hidden by optical extinction. The first indication of its nature was the discovery in 1931 by K. G Jansky that it was a strong source of radio emission.

The central region of the Galaxy contains two features that are particularly prominent in radio continuum maps, named Sagittarius A and Sagittarius B2.

One of the first signs that the Galactic center is a particularly interesting location in the Galaxy was the discovery that Sagittarius A encloses an intense, unresolved radio source known as Sagittarius A* (Sagittarius A star). The asterisk meant to convey its uniqueness and importance.

Sagittarius A* was discovered on February 13, 1974, by astronomers Bruce Balick and Robert Brown. They used a combination of the three element Green Bank interferometer with a 45 foot antenna located at a distance of 35 km in Huntersville West Virginia.

Using The Very Large Array in New Mexico in 1983, a team led by Ron Ekers saw the first time a ‘mini-spiral’ of hot gas surrounding Sagittarius A*.

In 1999 astronomers made an astonishing discovery. Sagittarius A* is a supermassive black hole more than four millions times more massive than the sun.

Study by Shanghai Astronomical Observatory found that the size of Sagittarius A* could fit between the Earth and the Sun.
Discovery of Sagittarius A*