Astronomers study the oldest observable stars in the universe in much the same way that archaeologists study ancient artifacts on Earth. Stellar archaeologist Anna Frebel is credited with discovering several of the oldest and most primitive stars, and her book, Searching for the Oldest Stars is a gripping firsthand account of her work. Recently she took the time to answer some questions:
What is your main research topic and what is stellar archaeology?
AF: My work is broadly centered on finding the oldest stars in the universe and using them to explore how the first stars and the first galaxies formed soon after the Big Bang. This works because these ancient stars are about 13 billion years old and they are still shining. The universe itself, by comparison, is 13.8 billion years old. I find these ancient stars in the outskirts of the Milky Way galaxy, using a large telescope. I’m also researching how the chemical elements heavier than hydrogen and helium were first created in those early stars, which ultimately allowed Earth to form and to bring about life in the universe.
What is your biggest discovery?
AF: I have been fortunate enough to discover several “record holding stars”. In 2007, I found a 13.2 billion year-old star, which is incredibly old. This followed the 2005 discovery of the chemically most primitive star – a star of the second generation of stars to have formed in the universe. Since then, I have analyzed some incredible ancient stars in dwarf galaxies that orbit the Milky Way galaxy, and together with my team, we have recently beaten said 2005 record, which was enormously exciting.
Why do people say we are made from stardust?
AF: We humans are made from all sorts of different chemical elements, mostly carbon. We breathe oxygen and nitrogen, we wear silver and gold jewelry. All these elements were once, atom by atom, created inside different kinds of stars and their supernova explosions over the course of billions of years. Studying this evolution of the chemical elements in the universe with the help of ancient stars means that I’m literally studying the cosmic origins of the building blocks of life. So we really are closely connected with the universe, far more than we realize.
How did you decide to become a scientist?
AF: From a young age I knew I wanted to study stars. They were just so fascinating to me, these big spheres of gas, fusing new elements to gain energy to shine for eons in the sky. Fortunately, I received good advice during high school on how to become an astronomer. After studying physics until 2002, I turned to astronomy and the rest is history. Today, I take pride in sharing my story with young people and the general public by telling them what astronomers do on a daily basis, and how scientific results are achieved. I am passionate about conveying the importance of science literacy to the young and the young at heart while inspiring them with the beauty and mystery of the cosmos.
What kind of telescope is used for your astronomical observations?
AF: Astronomers use all kinds of different telescopes on Earth as well as from space to peer deep into the cosmos. It depends on the type of project and the brightness of the objects which telescope is best suited. Space observations are being carried out remotely, whereas ground-based observations are still done by the astronomer who has to travel to the telescope. More and more telescopes are becoming automated to enable remote controlled “office observing”.
Anna Frebel in front of the 6.5m Magellan Telescope in Chile.
Are you traveling to any telescopes?
AF: Yes, I regularly fly to Chile to the Magellan Telescopes to carry out my observations. These are some of the largest telescopes in the world and the dark night sky in the Southern Hemisphere is terrific for studying the cosmos. It’s the favorite part of my job and I love discovering new facts about the universe through these observations!
What does it mean when you say you’re going observing?
AF: To use the telescopes, you have to fly to Chile. First to Santiago, then to La Serena and from there is a 2-3h drive up the mountains of the Atacama Desert where the telescopes are. There are guest rooms there for the observers to sleep during the day and the observatory chefs are cooking delicious meals for everyone. Dinner is eaten together by all observers, including the technical staff. It’s a little community with the sole purposes of caring for the telescopes and obtaining exquisite astronomical observations all night long of a breathtaking sky.
What does a typical night at the telescope look like?
AF: All preparations for the night happen during the afternoon while it’s still light outside. After sunset, I usually choose the first targets from my list, which I begin to observe soon after dark. Each star is observed for 10-30 minutes. We immediately inspect each observation and then decide on the fly whether we need more data or not. If we have found an interesting old star we may choose to immediately observe it for a few more hours.
Did anything ever go wrong at the telescopes?
AF: Of course! Mostly when it’s cloudy because then we can’t observe any starlight. This can be very frustrating because it can mean that we have to come back to the telescope a year later to try again. Clouds spell bad luck. Other times, the air layers above the telescope are often not as smooth as is required. This makes the stars twinkle and appear less sharp, which means less good data and longer exposure times. And sometimes there are technical problems with the telescope too.
How do you get your telescope time? Can I go to your telescope and observe, too?
AF: To obtain telescope time, astronomers have to submit a proposal to a committee that selects the best projects and awards them the time. The proposal contains a detailed description of the project and the technical details on what information is being sought. Telescope use is restricted to professional astronomers because of the considerable expense. The cost is about USD 50,000 to 100,000 per night, depending on the telescope, and often paid by various institutions and universities who jointly operate observatories. While this is a lot of money, it’s actually not that much in comparison to many other research facilities.
Are there any special moments at the telescope that you remember in particular?
AF: Yes, going observing is always magical and memorable. Of course I particularly remember big discoveries and the excited nervousness of checking and checking whether we didn’t make a mistake and that the discovery was really what it appeared to be. Then, there have been the frustrating moments of sitting at the telescopes for nights on end listening to the rain and flying home empty-handed. I have been there when severe technical problems and even a bush fire prevented observing during clear nights. But I always associate observing with the most colorful sunsets, the calm and peaceful atmosphere up in the mountains, and of course the sleepless but exciting nights.
Anna Frebel is the Silverman (1968) Family Career Development Assistant Professor in the Department of Physics at the Massachusetts Institute of Technology. She is author of Searching for the Oldest Stars, and has received numerous international honors and awards for her discoveries and analyses of the oldest stars. She lives in Cambridge, Massachusetts.
