Andrea M. Ghez

Andrea M. Ghez is an American astronomer who shared the 2020 Nobel Prize in Physics for discovering a supermassive compact object at the Milky Way’s center.

Reinhard Genzel: A German astrophysicist who shared the 2020 Nobel Prize in Physics for research on the Milky Way’s central compact object. Genzel led an independent observational program that reached the same conclusion as Ghez’s group.
Adaptive optics: A technique that corrects telescope-image distortions caused by Earth’s atmosphere using rapidly adjusted optics. It sharpened Keck images enough to distinguish crowded stars near the Galactic Center.
Sagittarius A*: The compact radio source associated with the supermassive black hole at the center of the Milky Way. Stars tracked by Ghez orbit this source, whose mass and compactness identify it as a black hole.
Black hole: A region of spacetime whose gravity is strong enough that nothing, including light, can escape beyond its event horizon. The compact object inferred from the stellar orbits is understood to be a supermassive black hole.
Roger Penrose: A British mathematical physicist whose work on black-hole formation earned him half of the 2020 Nobel Prize in Physics. He shared the Nobel with Ghez and Genzel, whose observations established a supermassive black hole candidate.
Infrared astronomy: The study of celestial objects through infrared radiation, which has wavelengths longer than visible light. Infrared observations penetrate dust that obscures the Milky Way’s central region in visible light.
S0-2: A young, massive star that completes a roughly 16-year orbit around Sagittarius A*. Its close passage around the center provided an especially informative test of the inferred mass.
Supermassive black hole: A black hole with a mass ranging from hundreds of thousands to billions of solar masses. The Milky Way’s central object belongs to this class, with about four million solar masses.
UCLA Galactic Center Group: A UCLA research team that studies the stars and compact objects near the Milky Way’s center. Ghez’s group used this team’s long-running observations to track stars near Sagittarius A*.
Stellar orbit: The path followed by a star as it moves under the gravitational influence of other masses. Measuring stellar orbits revealed how much mass was concentrated at the Galactic Center.

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