Ghez, Andrea

Andrea Ghez, in full Andrea Mia Ghez, (born June 16, 1965, New York, New York), American astronomer who was awarded the 2020 Nobel Prize for Physics for her discovery of a supermassive black hole at the centre of the Milky Way Galaxy. She shared the prize with British mathematician Roger Penrose and German astronomer Reinhard Genzel. She was the fourth woman to receive the Nobel Prize for Physics, after Marie Curie (1903), Maria Goeppert Mayer (1963), and Donna Strickland (2018).

Ghez received a bachelor’s degree in physics from the Massachusetts Institute of Technology in 1987 and a doctorate in the same subject from the California Institute of Technology in 1992. She was a postdoctoral fellow at the University of Arizona from 1992 to 1993, and she then became an assistant professor in physics and astronomy at the University of California, Los Angeles, in 1994. She became a full professor in 2000.

Ghez began her career in astronomy studying young binary stars using the technique of infrared speckle imaging, which removes the blurring Earth’s atmosphere imposes on astronomical images by taking many pictures with very short exposure times and adding them together. Beginning in 1995, Ghez and her collaborators began using speckle imaging and later adaptive optics (which moves the telescope mirror to compensate for atmospheric distortion) at the Keck Observatory in Hawaii to study stars near the centre of the Milky Way Galaxy. (Genzel and his collaborators performed similar observations at the same time with the New Technology Telescope and the Very Large Telescope in Chile.) With the improved resolution, they could identify individual stars and follow their orbits around the galactic centre. They found that the centre of the galaxy was coincident with the bright radio source, Sagittarius A*. The dark central object has a mass about 4 million times that of the Sun and is too small to be an extended source like a stellar cluster. Sagittarius A*, the centre of the galaxy, is thus a supermassive black hole.