Skip to content
Nobel Jews
Portrait of Andrea Ghez
Photo: BorderlineRebel, Own work · CC BY-SA 4.0 via Wikimedia Commons

Nobel Prize in Physics · 2020

Andrea Ghez

She tracked stars racing around the Milky Way's center and helped show that a black hole of four million suns sits there.

The Nobel citation: “for the discovery of a supermassive compact object at the centre of our galaxy”
Born
June 16, 1965, New York, NY, USA
Shared with
Roger Penrose, Reinhard Genzel
Affiliation at the time
University of California, USA

Physics prize

2020

Shared with 2 other laureates.

Age that year

55years

Born in 1965.

Sources cited

28

Fact-checked September 24, 2026.

  • In 1995 her first request for Keck telescope time to track stars at the galaxy's center was turned down. She borrowed time from another astronomer and applied again.
  • Her favorite star, S0-2, circles the Milky Way's black hole in about 16 years. The Sun needs more than 200 million years to circle the galaxy once.
  • Her father was born in Rome in 1938, the year Fascist Italy passed anti-Jewish laws. His Jewish family, with roots in Tunisia, left Italy and spent most of the war in New York.
  • In 2020 she became only the fourth woman to win the Nobel Prize in Physics, after Marie Curie, Maria Goeppert Mayer and Donna Strickland.
  • The starlight she studies left the black hole's neighborhood about 26,000 years ago. She has said that thought amazes her every time she goes to the telescope.

The breakthrough

Weighing the Milky Way's central black hole by tracking its stars (1995-2008)

At the center of our galaxy, about 26,000 light-years away, sits a radio source called Sagittarius A*. Astronomers had long suspected it was a giant black hole, but thick dust hides the region from ordinary telescopes, and Earth's shimmering air blurs the view. Starting in 1995, Ghez's team at UCLA looked in infrared light, which passes through much of the dust, using the 10-meter Keck telescope in Hawaii. She persuaded Keck's engineers to reprogram a camera to take very short exposures, which her team stacked to freeze the twinkling, a method called speckle imaging. Later they used adaptive optics, a flexible mirror that reshapes itself about 1,000 times a second to undo the blurring. Tracked year after year, some stars raced along at more than 1,000 kilometers per second. In 1998 the team showed that a dark mass of millions of suns sat in a space too small to be anything but a black hole. By 2003 they had followed one star, S0-2, far enough to pin down its roughly 16-year orbit. Using the same laws of motion that describe planets circling the Sun, they weighed the hidden object at about four million suns, packed into a region no larger than our solar system. Think of dancers whirling around a partner hidden in the dark: their speed and paths tell you how heavy the partner must be. Reinhard Genzel's team in Germany reached the same answer independently.[2],[3],[4],[5],[9],[10],[11],[12],[13],[15]

“I see being a scientist as really fundamentally being a puzzle solver.”
Andrea Ghez, Nobelprize.org interview on International Women's Day, 8 March 2021, describing her childhood love of jigsaw and crossword puzzles.[6]

What it meant for humanity

Ghez's work does not cure disease or grow food. What it gives is knowledge about our home in the universe. The question of what powers the radio source at the Milky Way's center had been debated for more than a quarter century, and the Nobel committee said the work of Ghez and Genzel gave the most convincing evidence yet that it is a supermassive black hole. From the orbit of the star S0-2, her group also measured our distance to the galactic center: about 8,000 parsecs, or roughly 26,000 light-years. Our galaxy's black hole became the closest example of the giant black holes that appear to sit at the centers of most large galaxies, and a laboratory for testing gravity. In 2019 her team showed that light from S0-2, as it swung close to the black hole in 2018, was stretched just as Einstein's general relativity predicts, and ruled out a Newtonian model with high statistical confidence. Her results also raised new puzzles. Young, massive stars orbit close to the black hole, where theories said stars could not form, a problem her team called a paradox of youth. When the Event Horizon Telescope released the first image of Sagittarius A* in 2022, its interpretation rested partly on the star orbits measured by the Ghez and Genzel teams. Her demands also pushed Keck's engineers to adapt their instruments, part of a cycle in which new science questions drive new telescope technology. She has shaped people too. She has trained many students at UCLA, chose to teach introductory physics to reach more young women, published the book You Can Be a Woman Astronomer in 1995, and in 2020 became the fourth woman to win the Nobel Prize in Physics.

  • Her 1998 study of 90 stars found a dark mass of about 2.6 million suns packed so tightly that no realistic star cluster could explain it, pointing to a central black hole.[13]
  • By tracking the star S0-2 around its 16-year orbit, her team weighed the black hole at about 4 million suns and measured our distance to the galactic center.[4],[15],[16]
  • In 2019 her team showed that S0-2's light is stretched near the black hole as general relativity predicts, ruling out a Newtonian model at five-sigma confidence.[10],[17]
  • ESO said the star-orbit research led by Genzel and Ghez gave a strong basis for interpreting the first image of Sagittarius A*, released in 2022.[18]
  • Keck Observatory's director wrote that her constant push for better performance, and his engineers' answers to it, helped make adaptive optics the powerful tool it is today.[12]

Impact in numbers

Ghez's contribution is knowledge, not a product. With Genzel's team she helped settle whether our galaxy has a giant black hole at its heart, turned the galactic center into a laboratory for testing Einstein's theory of gravity, and raised new questions about how stars can form so close to such an object. None of this has a credible dollar value or count of lives, so we record no quantified claims. Her persistence also pushed telescope technology forward at Keck, but adaptive optics was first proposed by others decades earlier; she was an early and demanding user, not its inventor, so crediting her with its wider uses would overstate her role. Her wider impact is on people: the students she has trained and the young women who see a path into physics through her example.

Fundamental scienceSpaceTechnologyEducation

No number is given here on purpose. Some contributions cannot be counted honestly, and we would rather describe them than invent a figure.

The double edge

No harms are documented from Ghez's discovery itself. It is basic research with no military or commercial use. The main controversy concerns where this kind of astronomy is done. Her observations were made with the Keck telescopes on Maunakea in Hawaii, a summit that many Native Hawaiians hold sacred. When protesters blocked construction of the Thirty Meter Telescope there in 2019, police arrested 38 elders, most of them Native Hawaiian. In 2020 Ghez, a member of the project's advisory committee, briefed University of California regents on the telescope and argued that Maunakea was the best location for its science. She has also said that research integrity means understanding the social implications of one's work, and that scientists should take part in ethical debates about how discoveries are used. In 2022 Hawaii created a new governing authority for the summit that gives Native Hawaiian cultural experts voting seats.

  • Moderate

    Backing a giant telescope on a sacred mountain

    Ghez's discoveries depend on telescopes atop Maunakea, which many Native Hawaiians consider sacred. As a member of the Thirty Meter Telescope's advisory committee, she told University of California regents in 2020 that Maunakea is the best site for the project, which protesters blocked in 2019. She did not build Keck or decide the site, but she has publicly supported it.[26],[27],[28]

Against the odds

Ghez was born in New York in 1965 and grew up in Chicago, and no source records antisemitism aimed at her. The persecution in her story came a generation earlier. Her paternal grandfather, Henri Ghez, came from a Jewish family with roots in Tunisia and ran a rubber factory near Rome with his brother Oscar. In 1938 Mussolini's Fascist regime began passing anti-Jewish laws that pushed Jews out of government jobs (public-school teaching included), the armed forces and the media, banned marriages between Jews and non-Jews, and interned foreign Jews. Thousands of Italian Jews emigrated, mostly to the Americas. The Ghez brothers traded their factory for one near Lyon, and the family took refuge in the United States. Ghez's father, born in Rome in 1938, spent most of the war in New York. After Germany occupied Italy in 1943, it deported more than 8,500 Jews from Italy and Italian-held lands, most of them to Auschwitz. Ghez's own obstacles were those of a woman in physics. Some people told her that a girl could not get into MIT, and similar doubts met her application to Caltech. Later she chose to teach introductory physics partly because so few women were in those classes. In 1995 her first proposal to track stars at the galaxy's center was turned down, and she found telescope time another way.

  • 1938

    Persecution

    Fascist Italy's 1938 anti-Jewish laws pushed Jews out of government jobs, including public-school teaching, and out of the armed forces and the media. Her grandfather's Jewish family, of Tunisian origin, left Italy, and her father, born in Rome that year, spent most of World War II in New York.[19],[20],[23]

  • 1939

    Exile

    Facing the racial laws, her grandfather Henri and his brother Oscar exchanged their rubber factory near Rome for a Pirelli plant near Lyon. During World War II the Ghez family took refuge in the United States.[21],[22],[25]

  • —

    Discrimination

    Some people told her a girl could not get into MIT, and similar doubts greeted her application to Caltech's doctoral program. In graduate school she noticed how few women were in introductory physics classes and chose to teach them.[6],[11]

Jewish background

Jewish fatherRelationship to Jewish identity not documented

Ghez's father, the economist Gilbert Ghez (1938-2015), was born in Rome to Henri Ghez and Elsie Marx of Frankfurt. The Ghez side was a Jewish family of Tunisian origin, and after Fascist Italy's 1938 anti-Jewish laws the family left Italy and spent most of World War II in New York. Her mother, the Chicago art curator Susanne Ghez, grew up in an Irish Catholic family in Massachusetts and had 12 years of Catholic schooling. Jewish media noted Ghez's Jewish heritage when she won the Nobel Prize, but in the sources we found she has not publicly discussed a Jewish or other religious identity.[19],[20],[21],[22]

Key dates

  1. 1938

    Her father, Gilbert, is born in Rome to a Jewish family of Tunisian origin. Fascist anti-Jewish laws passed that year drive the family out; they spend most of the war in New York.[19],[20],[23]

  2. June 16, 1965

    Born in New York City, the eldest of three daughters of Gilbert Ghez, an economist, and Susanne Ghez, who later directed a Chicago contemporary art gallery.[1],[6],[11],[21]

  3. 1969

    Her father joins the University of Chicago and the family moves to Chicago. The Apollo moon landing, when she is four, sparks her interest in space.[6],[20]

  4. 1987

    Earns a bachelor's degree in physics from MIT, having started college as a math major.[6],[10]

  5. 1992

    Earns her PhD at Caltech, studying young stars under infrared-astronomy pioneer Gerry Neugebauer.[2],[11]

  6. 1994

    Joins the UCLA faculty after one year at the University of Arizona as a Hubble Fellow.[10],[11]

  7. 1995

    Begins imaging stars at the galactic center with the 10-meter Keck telescope in Hawaii, after her first proposal for the project is turned down.[7],[11],[13]

  8. 1998

    Publishes evidence from the motions of 90 stars that the Milky Way harbors a central black hole of millions of suns.[10],[13]

  9. 2000

    Reports in Nature the first measured accelerations of stars orbiting the black hole.[10],[14]

  10. 2003

    Measures the spectrum and orbit of the star S0-2, weighing the black hole at about 4 million suns and finding young stars where none were expected.[10],[15]

  11. 2008

    Named a MacArthur Fellow.[10]

  12. 2012

    Shares the Crafoord Prize in astronomy with Reinhard Genzel, becoming the first woman to win it.[11],[24]

  13. 2019

    Her team shows in Science that S0-2's light is stretched near the black hole just as Einstein's general relativity predicts.[10],[17]

  14. October 6, 2020

    Shares half of the Nobel Prize in Physics with Reinhard Genzel; Roger Penrose receives the other half. She gives her Nobel lecture online on 8 December.[2],[8]

Sources

  1. 1.Andrea Ghez - Facts · NobelPrize.org (Nobel Prize Outreach)
  2. 2.Press release: The Nobel Prize in Physics 2020 · NobelPrize.org (Royal Swedish Academy of Sciences), 2020
  3. 3.Popular information: Black holes and the Milky Way's darkest secret · NobelPrize.org (Royal Swedish Academy of Sciences), 2020
  4. 4.Scientific Background on the Nobel Prize in Physics 2020: Theoretical foundation for black holes and the supermassive compact object at the Galactic centre · Nobel Committee for Physics, Royal Swedish Academy of Sciences, 2020
  5. 5.Andrea Ghez - Interview (telephone interview after the announcement, 6 October 2020) · NobelPrize.org, 2020
  6. 6.Interview with Andrea Ghez, March 2021: "I see being a scientist as being a puzzle solver" · NobelPrize.org, 2021
  7. 7.Transcript from an interview with Andrea Ghez (Nobel Week, 12 December 2022) · NobelPrize.org, 2022
  8. 8.Andrea Ghez - Nobel Lecture: From the Possibility to the Certainty of a Supermassive Black Hole · NobelPrize.org, 2020
  9. 9.The Nobel Prize in Physics 2020 - Award ceremony speech · NobelPrize.org, 2020
  10. 10.Andrea Ghez wins 2020 Nobel Prize in physics (Stuart Wolpert) · UCLA Newsroom, 2020
  11. 11.A Search for Knowledge That Led Andrea Ghez to a Nobel Prize · UCLA Magazine (UCLA Newsroom), 2021
  12. 12.How Andrea Ghez Won the Nobel for an Experiment Nobody Thought Would Work (Hilton Lewis, director of W. M. Keck Observatory) · Scientific American, 2020
  13. 13.High Proper Motion Stars in the Vicinity of Sgr A*: Evidence for a Supermassive Black Hole at the Center of Our Galaxy (Ghez, Klein, Morris and Becklin; Astrophysical Journal 509, 678-686) · arXiv / The Astrophysical Journal, 1998
  14. 14.The Accelerations of Stars Orbiting the Milky Way's Central Black Hole (Ghez, Morris, Becklin, Tanner and Kremenek; Nature 407, 349) · arXiv / Nature, 2000
  15. 15.The First Measurement of Spectral Lines in a Short-Period Star Bound to the Galaxy's Central Black Hole: A Paradox of Youth (Ghez et al.; Astrophysical Journal Letters 586, L127) · arXiv / The Astrophysical Journal Letters, 2003
  16. 16.Measuring Distance and Properties of the Milky Way's Central Supermassive Black Hole with Stellar Orbits (Ghez et al.; Astrophysical Journal 689, 1044-1062) · arXiv / The Astrophysical Journal, 2008
  17. 17.Relativistic redshift of the star S0-2 orbiting the Galactic center supermassive black hole (Do, Hees, Ghez et al.; published in Science, 2019) · arXiv / Science, 2019
  18. 18.Astronomers reveal first image of the black hole at the heart of our galaxy (eso2208) · European Southern Observatory, 2022
  19. 19.Scientists of Jewish heritage among trio to win Nobel prize for black hole finds · The Times of Israel (AP and ToI Staff), 2020
  20. 20.Gilbert Ghez obituary (1938-2015) · Chicago Tribune (via Legacy.com), 2015
  21. 21.Oral history interview with Susanne Ghez, 2011 Jan. 25-26 · Archives of American Art, Smithsonian Institution, 2011
  22. 22.Regards d'un collectionneur: the collection of Oscar Ghez (6 key dates about Oscar Ghez) · Caumont-Centre d'Art, Aix-en-Provence, 2025
  23. 23.Italy (Holocaust Encyclopedia) · United States Holocaust Memorial Museum
  24. 24.Andrea Ghez - Crafoord Prize in Mathematics and Astronomy 2012 · The Crafoord Prize (Royal Swedish Academy of Sciences), 2012
  25. 25.Oscar Ghez · Wikipédia (French)
  26. 26.UC Board of Regents discusses Thirty Meter Telescope on Maunakea · The Daily Californian, 2020
  27. 27.Native Hawaiians gain more authority over future of sacred mountain, astronomy site (Associated Press) · PBS NewsHour, 2022
  28. 28.Opinion: Thirty Meter Telescope research must consider sanctity of Native Hawaiian land · Daily Bruin, 2023

Fact-checked on September 24, 2026 by a separate AI fact-checking pass that re-opened the sources, with 8 corrections made. How we check

Suggest a correction