Q&A: Black Holes

Q:
I was hoping you could tell me the date scientists confirmed the presence of the black hole in the center of the Milky Way?

A:
In 1971 Donald Lynden-Bell and Martin Rees suggested that the center of our galaxy should contain a supermassive black hole. In 1974, Bruce Balick and Robert Brown found a compact radio source there. This source came to known as Sagittarius A* (Sgr A*) to distinguish it from more a extensive radio source Sgr A in the same region. Infrared observations in the 1980s strengthened the case for a supermassive black hole.

The most recent breakthrough has been provided in the last 6 years by infrared images from the European Southern Observatories' New Technology Telescope (A. Eckart and R. Genzel) and the Keck Telescope (Andrea Ghez and collaborators). These results suggest a black hole with a mass of 2.6 million solar masses.

Recently (September 2001) Fred Baganoff and collaborators used the Chandra X-ray Observatory to observe an X-ray flare that brightened in about ten minutes provided more strong evidence for a black hole. It is difficult to imagine any other type of object that could flare up so brightly in so short a time.