What do you do as an astronomer?
In general, astronomers try to determine the origin and nature of our universe. I study galaxies and black holes within galaxies. My interests center on how galaxies form, how they evolve, and why some galaxies contain black holes in their centers.
What are galaxies and black holes?
Galaxies are the main building blocks of the visible universe. They are each composed of approximately 100 billion stars bound together by their mutual gravitational attraction. Some galaxies have in their centers a very massive object known as a black hole.
The term “black hole” is a bit of a misnomer; it isn’t a hole at all. It is an object whose gravitational pull is so strong that matter and light cannot escape. One type of black hole is formed from a star that collapses when its fuel runs out. Normally, the heat generated by the burning of a star’s fuel provides a pressure out from the center of the star, which counteracts the inward pressure from gravity. If the fuel runs out, the star, if sufficiently massive, can collapse under its own weight.
Supermassive black holes in the centers of galaxies—the type I am studying—are formed in a very different way. We have several theories about how they might be formed, but we’re not yet sure which is right.
What are some of the theories?
One theory is that supermassive black holes were formed shortly after the Big Bang. When matter was initially expanding, there were some wrinkles in space—uneven clumpings of gas. The biggest clumps might have collapsed in on themselves due to gravity and formed supermassive black holes.
Another idea is that they might have formed from individual stellar black holes—the type I described earlier. The centers of galaxies contain an enormous number of stars packed together in a tiny area. Under these conditions, stellar-sized black holes might merge together into one very massive black hole. They would condense there like heavy liquids settling at the bottom of a cup.
How do you detect a black hole?
Although black holes are, by definition, invisible, you can pinpoint them by trying to detect their gravitational influence on objects in their vicinity. Just as we could infer the presence and the mass of the sun, even if it were unseen, by tracing the orbits of the planets, we can deduce the existence of black holes by carefully measuring the motions of stars and interstellar gas clouds whirling around them.
What kind of data do you use?
I use data from many different telescopes around the world (Hawaii, New Mexico, Chile) and in space (the Hubble Space Telescope) to collect radiation from different parts of the electromagnetic spectrum, which ranges from radio waves to visible and ultraviolet light to X-rays. These data are used to determine the physical make-up and inner workings of the central regions of galaxies.
Have you always been interested in astronomy?
Well, I’ve always been interested in the “big questions.” In high school I really loved cell biology. I participated in many science fairs, tinkered with just about anything that could be grown in my bedroom, and sought out various enrichment programs at universities during the summer.
As an undergrad at Harvard, I became more interested in wider philosophical issues: I was engrossed with philosophy, especially topics that attempted to address human nature and our place in the universe. I stumbled upon astronomy one day during my sophomore year at an informal seminar. I was convinced that I had finally found the grandest of the sciences, the noblest of pursuits.
You seem to be just as enamored of astronomy now as you were in college.
It is such an exciting field. Although it is an ancient science, it’s also a very new field. Because so much is still unknown and progress is so rapid, I was confident that one person could make meaningful, lasting contributions to the field.
On one of the many nights I spent at Lick Observatory on Mt. Hamilton, near San José in California, I went outside my dome to inspect the weather. That night the air was exceptionally calm, the sky perfectly clear. Out in the distance stretched San José, enveloped in a canopy of orange glow emanating from the city’s sodium lights. For the first time I realized how beautiful it was to hear absolute silence. The whole world was asleep—everybody except me. And I realized that I was in control of this mighty telescope. I can point it to any star, any galaxy I want. I can use it to peer into the outer reaches of the cosmos and ask all the big questions. What a wonderful privilege this is, I thought, and I still think so.
What did you study in college to prepare for your career?
I earned joint degrees in astronomy and physics. Astronomy requires a solid background in physics and mathematics. It is impossible to do serious research in astronomy without a thorough understanding of physics. Since I was taking so many physics courses anyway, I took a few extra to fulfill the requirements of the physics curriculum. Because I double-majored, I developed a broader understanding of electromagnetism, gravity theory, and classical and quantum mechanics, which were invaluable supplements to my studies in astronomy.
Did you get a chance to do any research while you were an undergraduate?
Yes. I was fortunate to have good mentors in college, and I took advantage of all the opportunities that came my way. By volunteering most of my free time at the university’s observatory, I was able to work on research projects very early on. My most concentrated effort was to study the center of our own galaxy, the Milky Way, which we now know houses a supermassive black hole with a mass three million times that of the sun.
What projects are you working on now?
I am using the Hubble Space Telescope to image the centers of nearby galaxies and observe the effect that black holes have on their surroundings. I am also very interested in the starburst phenomenon, in which very large numbers of stars form over a short period of time in neighboring galaxies. Cosmic firecrackers, if you will.
What do you see as the most rewarding aspect of your career in astronomy?
There are many aspects that are very satisfying, but perhaps the most rewarding is my complete independence in my work. One of the greatest satisfactions related to this independence is that I can honestly say that I’ve never really wanted to take a vacation! To me, there is no distinction between my activities at work and outside of work. My study of astronomy isn’t limited to my office—it follows me home. Often I have dinner with it; I sleep with it; I dream about it; I wake up with it. Sometimes I am so engrossed with a particular problem that it stays on my mind for days on end.
I also travel quite a bit—sometimes to very remote parts of the world—to collect data and attend conferences. I just spent two weeks in Japan, and I’m going to India shortly to attend a month-long workshop on black holes.
As much as I love what I do, I also feel I have a tremendous responsibility to society. Scientists have an obligation to the public at large: to inform, to educate, and to inspire.
What do you think is the most exciting facet of astronomy?
The fact that the whole field is making advances at a dizzying pace. We are fortunate to be living in an era of technological explosion, and as a result, telescopes that are more powerful than ever are sprouting up across the globe, and others are being prepared to be launched into space. In this way, the oldest of the sciences continues to renew itself.
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