Tam on STEAM
Note: On Oct. 6, 2020, Andrea Ghez was awarded the Nobel Prize in Physics for “the discovery of a supermassive compact object at the center of our galaxy.” She shares the prize with Reinhard Genzel of UC Berkeley and the Max Planck Institute for Extraterrestrial Physics and Roger Penrose of the University of Oxford.
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Andrea Ghez still remembers reading the article posted on a wall at her high school. A scientific study had concluded that boys were smarter than girls at math.
Ghez didn’t buy it. She loved math. So she challenged the boys in her math class to a contest to see who could do better on tests. Who won? “I did pretty well,” Ghez says with a laugh.
Math problems weren’t the only challenges that captured her imagination. She relished all types of puzzles—jigsaw puzzles, crossword puzzles, logic puzzles. And she often found herself pondering the more profound puzzles: How did time begin? Where is the edge of the Universe? And what is our place in the vast cosmos?
Ghez kept looking for answers as she built a career as a professor of physics and astronomy at the University of California, Los Angeles. There, she and her team helped to solve one of the biggest mysteries in astronomy. They used a new imaging technique to provide strong evidence that a supermassive black hole lies at the center of our galaxy.
Along the way, Ghez became a leader in the world of astrophysics, winning dozens of honors and prizes, including a MacArthur “Genius” Fellowship. Discover magazine named her one of the Top 20 young American scientists. She has embraced her high visibility as a way to open people’s minds about the possibilities for women in science.
DANCING AND DREAMING
The future astronomer grew up in Chicago, where her father was a professor of economics and her mother was director of a contemporary art gallery.
Ghez was a responsible, somewhat shy child. She took dance lessons and thought about becoming a ballerina. She also followed the Apollo space missions and dreamed of being an astronaut. Her mother encouraged her to dream big and to push herself to achieve her goals.
A voracious reader, Ghez gravitated to Isaac Asimov’s essays on the cosmos and books about Marie Curie and Amelia Earhart. She also devoured mystery novels. “I think I always had that love of solving mysteries and puzzles, which is so relevant to being a scientist” she said.
In high school, Ghez excelled in math and science. She remembers being encouraged by her chemistry teacher—“one of the only female science teachers I ever had.” Ghez balanced her academic activities by competing in track and playing on the field hockey team.
THE ASTROPHYSICS BUG
By the time she was ready for college, Ghez knew she wanted to go into a STEM field. She decided on the Massachusetts Institute of Technology in Cambridge. At first she intended to major in math. But then, she said, she discovered that “physics was the running theme in everything.” She switched to physics and began doing research on cosmic sources of x-rays.
She spent summers working at telescopes in Arizona and Chile. Working in those older observatories was very different from using today’s computerized systems. She had to keep the telescope centered with a hand paddle as she looked through the eyepiece.
She had found her passion. “I started doing research in astrophysics and got the bug,” she said. “I reconnected with that sense of wonderment. We live in this huge universe, and we’re so tiny. Going to the telescope reminds you of that.”
THEY HAD HER BACK
After receiving her B.S. in physics in 1987, Ghez headed west to the California Institute of Technology in Pasadena, known for its great astrophysics program. She studied the birth of stars—particularly binary stars, which form in pairs.
Ghez worked under the guidance of the eminent astronomers Gerry Neugebauer and Anneila Sergant. They and other mentors helped her make her way in a field dominated by men.
“When I was a student, there were very few women faculty,” she said. “It was hard to envision myself in that role. I felt like I was on the wrong playground.” Her advisors made the difference, she added: “That’s the most important decision you can make—choosing great mentors who are capable of supporting your professional development.”
Ghez received her Ph.D. in physics in 1992 and joined the faculty at UCLA in 1994.
THE ULTIMATE PUZZLE
Being in the University of California system gave Ghez access to the powerful Keck telescope on the top of Mauna Kea in Hawaii. She wanted to use the telescope to solve a mystery at the heart of our galaxy.
Scientists had theorized that the Milky Way revolves around a supermassive black hole. A black hole is a region of space so dense that not even light can escape its gravity. So we can’t see it. The challenge for Ghez was how to make the invisible visible.
Ghez and her team of graduate students faced an obstacle familiar to all astronomers using land-based telescopes—Earth’s atmosphere blurs their view of objects in space. Then Ghez came up with a way to use a laser to sharpen the telescope’s vision to capture the movement of stars near the galaxy’s center.
See BLACK-HOLE HUNTERS for more on Andrea Ghez’s research.
Ghez’s team visited Mauna Kea half a dozen times a year to capture new images. Working on the mountaintop meant dealing with altitude sickness and other hardships. “When you get to the summit, your brain doesn’t work very well in the first few days,” she said.
Still, staying at the Mauna Kea complex had its upside. “It was like being in a dorm in college,” Ghez said. “It was exciting—the adventure of being up there and meeting researchers from all over the world.”
By comparing images taken months and even years apart, the team was able to create time-lapse “movies” of the stars’ movements. The new technique revealed something amazing—the stars were spiraling at blinding speed around an incredibly dense object. It’s the best evidence yet of a supermassive black hole.
The discovery was huge news in the astronomy world. Ghez was proud of her role in helping to solve the mystery. “It’s fun just to be able to put a new piece of the puzzle forward,” she said. “Just moving our knowledge forward is what floats my boat.”
BACK ON EARTH
As Ghez continues to peer into the heart of the Milky Way, she faces the challenge of balancing her work with her life her on Earth. She is married to Tom LaTourrette, a geologist at the RAND Corporation. They have two sons, ages 10 and 14.
“It’s an evolving balancing act,” she said. “Your career doesn’t stay static, nor does your family.” She makes time to hang out with her sons, and she has started to bring them on work-related trips to expose them to the life of a scientist.
Always on her mind is her status as a role model. “I enjoy teaching introductory classes because you can have the biggest impact,” she said. “It’s a chance to influence the thinking of people about women in the sciences.”
Female students often seek her out, she said, and she welcomes the chance to encourage them. “I like to show students that this field is a possibility—and a possibility without sacrificing your personal life,” she said. “I make a point of sharing that I have kids.”
Ghez’s impact as a role model is strengthened by the fact that she is an animated and accomplished speaker. But that wasn’t always the case. “When I gave my first research seminar, every bone in my body shook,” she said. “Public speaking scared me more than anything else.”
The more times she delivered talks and lectures, though, the easier things got. “I learned to translate nervousness into excitement,” she said. “So today I don’t think twice about it.”
Talking about how she overcame stage fright to become a strong science communicator is just one more way that Ghez hopes to inspire young scientists: “I think that’s a useful message for young girls about not pigeonholing who they are or what they are capable of.”
Watch Andrea Ghez’s TED talk on the hunt for a supermassive black hole: Click Here
BLACK-HOLE HUNTER
Andrea Ghez had long dreamed of hunting for the supermassive black hole thought to lie at the center of the Milky Way. When she joined the faculty at the University of California, Los Angeles, in 1994, she finally had the right tool for the job.
Working at UCLA gave Ghez access to the 10-meter Keck telescope on the top of Mauna Kea in Hawaii. The Keck was the biggest of a new generation of telescopes, and the 14,000-foot peak of Mauna Kea is one of the best places on Earth to get a good view of the stars.
Scientists had theorized that all galaxies have black holes at their centers. A black hole is a region of space with gravity so intense that no matter or radiation—not even light—can escape.
Since black holes are invisible, Ghez explained, “The tool that we use is to watch stars that orbit a black hole.” There’s a problem, though. Earth’s atmosphere distorts our view of those distant stars.
Ghez compares the challenge to looking at a pebble at the bottom of a moving river. She needed to find a way, in effect, to make the “river” stand still.
In 1995, Ghez and a team of graduate students began using the Keck telescope to track the stars. They used infrared wavelengths to see through the heavy dust near the galaxy’s center, some 26,000 light-years away. They also developed a new technique called adaptive optics.
To overcome the atmosphere’s distortion, they aimed a powerful laser toward the sky to create an artificial “star” in the direction of the real star they wanted to observe. A computer tracked the distortion of the laser’s “star.” Then astronomers could correct for atmospheric distortion by shifting the surface of a flexible mirror. “It’s kind of like very fancy eyeglasses for your telescope,” Ghez said.
Her team returned to the Keck telescope over months and years, capturing images that they put together to create time-lapse “movies” of the stars’ movements. But it was slow work. It took five years of measurements just to confirm that the star closest to the galaxy’s center had turned a corner in its orbit.
At first the team worked on the mountaintop, struggling with the effects of high altitude. After a few years, they were able to control the telescope from the observatory’s facility at sea level in Waimea. Today they can operate the Keck telescope from UCLA.
To prove the existence of a supermassive black hole, Ghez said, “I want to see the stars that are as close to the center of the galaxy as possible, because I want to show there is a mass inside as small a region as possible.“
The researchers traced the movement of about two dozen stars orbiting at incredible speeds. They were able to follow one particular star, called S0-2, through its entire 16-year orbit.
Their measurements showed that S0-2 and other stars were orbiting something with an immense mass—equivalent to 4 million suns—in a relatively small area—as big as our solar system. It almost had to be a supermassive black hole. “There are no other alternatives that we know of,” Ghez said.
The confirmation was a breakthrough but not a surprise. But there was one big surprise in what Ghez and her team saw. Some of the stars were young. New stars should not exist near a black hole. In theory, any cloud of gas and dust would be torn to shreds before it could form a star. Ghez and other astronomers still can’t explain the presence of such young stars.
Recently Ghez has tracked a mysterious object called G2, discovered in 2011. Some astronomers thought it was a huge cloud of hydrogen gas. But then G2 swung past the supermassive black hole without being torn apart. That meant it could not be a gas cloud. Ghez concluded G2 is probably a pair of binary stars pulled together by intense gravity to form one huge star enveloped in gas and dust.
Ghez is looking forward to a unique opportunity in 2018, when the star S0-2 makes its closest approach to the galactic center. Scientists predict that a black hole will cause deviations from general relativity—Albert Einstein’s theory of gravity. This theory says gravity results from the distortion of space and time. Objects of greater mass cause more distortion of space-time.
“One of our ambitions is to test general relativity around a supermassive black hole,” Ghez said. S0-2’s close encounter with the galactic center will give her this chance.
Ghez continues to search for ways to get a clearer view of the heart of the Milky Way. “The technology keeps advancing,” she said. “With every step forward, we can see more and more.”