By Clara Medina '23
Andrea Ghez, born June 16, 1965, in New York City is an American astronomer and professor at UCLA. Gaining inspiration from the Apollo landings of 1969, Ghez pursued a career in science. She received a BS in physics from MIT and a PhD under her advisor, Gerry Neugebauer, at the California Institute of Technology. Ghez is highly accomplished in her field; she has received various awards, made multiple television appearances, and co-wrote a book titled “You Can Be a Woman Astronomer.” Among her most notable accomplishments include a Maria Goeppert-Mayer Award, Bakerian Medal, MacArthur Fellowship Grant, and a Nobel Prize in Physics. Ghez is only one of four female Nobel Prize winners in her field, thus an inspiration and icon in the female scientific community and the scientific field at large. She exhibits the intellectual capacity and tenacity to defy the odds and tackle more profound questions about the inner workings of the universe.
Research
Ghez began her research career with a background in imaging technology and a longstanding fascination with black holes and astronomy. For decades, scientists have questioned what was causing the radio light at the center of the Milky Way. While there have been suggestions of it being a supermassive black hole, the idea was controversial and seen as impossible to prove. Ghez dedicated her career to answering this one question; she tracked the stars closest to the center of the galaxy to see if she could forge any connections. However, there were several doubts about the success and feasibility of her work. Ghez's first proposal to observe the orbits of the stars was rejected. When she was finally able to utilize the telescopes, she had to prove that she could actually track the stars’ motion, while taking into account atmospheric turbulence. She pioneered a team in implementing several new technologies such as adaptive optics. Ghez developed a technique called speckle imaging which involves taking numerous short exposures of a star with high sensitivity, and then stacking the data to sharpen the image. While this helped to produce sharper images, the technology could only be used to sharpen the brightest stars. Ghez’s willingness to take calculated risks to improve her equipment while risking the possibility of breaking it is what allowed her to solve the problem of the obscuring effects of Earth’s atmosphere. Keck Observatory was one of the first to install adaptive optics into their telescopes. It is through the implementation of this technology under Ghez’s leadership that resulted in her award-winning findings.
Discovery & Significance
Ghez’s big discovery answered the question of what lurks at the center of the Milky Way. Her hypothesis, which would later earn her a Nobel Prize, was a supermassive black hole, which is four million times the mass of the sun and known as Sagittarius A*. Proving this was no easy feat, not only was the theoretical black hole twenty-four thousand lightyears away, it was also covered by spaced dust and thus invisible to direct observation. 14,000 feet above the Pacific Ocean, Ghez conducted her work using UCLA’s Keck Observatory’s twin telescopes in Mauna Kea, Hawaii. Keck’s adaptive optics technology, near-infrared camera, and OH-Suppressing infrared imaging spectrograph allowed her and her team to clearly track the orbits of stars around the black hole. In 2000, the team confirmed the first sighting of stars accelerating around the black hole, and in 2005, they captured the first clear picture of the center of the Milky Way. In 2018, Ghez and her team observed the star S2 passing by Sagittarius A* at 4,300 miles per hour or nearly three percent of the speed of light. Perhaps the most notable feature of S2 or S0-2 is the fact that added that her research team is one of only two groups in the world to watch a star known as S0-2 is that Ghez’s team has its full orbit, which is about 16 years, in three dimensions. This opened up the possibility of conducting further tests on general relativity and ultimately Ghez’s findings proved the theory’s validity. Einstein predicted that when light passes close to a powerful source of gravity, it doesn’t slow down but instead loses some of its energy. This causes a decrease in wavelength or a gravitational redshift as the light gets stretched due to the curvature of spacetime. Ghez’s observations of S2 directly aligned with Einstein’s predictions. These observations enabled Ghez to strengthen the evidence that there is in fact a supermassive black hole at the Milky Way’s center, responsible for the phenomenon first pioneered by Einstein.
Understanding and Perception of the Universe
Ghez shared one-fourth of her Nobel Prize with Professor Reinhard Genzel who worked on the team with her and one-half with Professor Roger Penrose who first proved the formation of black holes as a direct result of Einstein’s general theory of relativity. Penrose’s work served as a foundation for Ghez’s findings and our working knowledge surrounding black holes. He did not prove their existence, but he also described them in unprecedented great detail, stating that black holes hid a singularity in which all known laws of nature cease to exist. Ghez’s discovery was imperative to confirming Einstein’s century-old theory of general relativity about gravity being the result of the curvature of spacetime. However, Ghez’s observations only raise further questions about our perception of the universe. While Einstein’s theories were accurate in determining how objects due to gravity behave near a supermassive black hole, it lacks a complete explanation for the gravity inside and it’s only a matter of time before we develop a new, more detailed theory to explain the black hole’s complexities. As Ghez stated in one of her interviews, “the laws of physics and gravity should be valid in every single part of the universe therefore the inside of a black hole shouldn’t contradict this.”
References:
Bartels, Meghan. “Seeing the Invisible: How Nobel Laureate Andrea Ghez Found the Supermassive Black Hole in the Milky Way’s Center.” Space.com, 26 Mar. 2021, www.space.com/andrea-ghez-supermassive-black-hole-milky-way-diversity.
Borkar, Abhijeet. The Story of How Scientists Discovered the Black Hole at the Milky Way’s Centre – the Wire Science. 10 Dec. 2020, science.thewire.in/society/history/penrose-genzel-ghez-nobel-prize-physics-sagittarius-a-star-radio-emissions-eht/. Accessed 28 Feb. 2022.
Byrd, Deborah. “Update on S2, the Star Plunging Past the Milky Way’s Black Hole | EarthSky.org.” Earthsky.org, 2018, https://earthsky.org/space/star-s2-s0-2-single-milky-way-monster-black-hole/
“Einstein’s General Theory of Relativity Is Questioned but Still Stands ‘for Now’ – W. M. Keck Observatory.” W.M. Keck Observatory, 25 July 2019, keckobservatory.org/ghez-einstein/ . Estvanik Taylor, Nicole. “Alumna Andrea Ghez Wins Nobel Prize for Discoveries in Black Hole Physics.” Alum.mit.edu, 14 Oct. 2020, alum.mit.edu/slice/alumna-andrea-ghez-wins-nobel-prize-discoveries-black-hole-physics. Accessed 28 Feb. 2022.
Lewis, Hilton. “How Andrea Ghez Won the Nobel for an Experiment Nobody Thought Would Work.” Scientific American, 8 Oct. 2020, www.scientificamerican.com/article/how-andrea-ghez-won-the-nobel-for-an-experiment-nobody-thought-would-work/.
Resnick, Brian. “How a Star Orbiting a Supermassive Black Hole Proves Einstein Is (Still) Right about Gravity.” Vox, 26 July 2018, www.vox.com/science-and-health/2018/7/26/17616904/supermassive-black-hole-sagittarius-einstein-relativity-eso-very-large-telescope. Accessed 28 Feb. 2022.
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