In her 15-year career as a “planet hunter,” Yale professor Debra Fischer estimates that she has discovered at least “a few hundred” worlds outside our solar system, though she has long since stopped keeping track of the exact number. The founder and leader of the Yale Exoplanet Group, Fischer co-discovered the first multi-planet system beyond our own solar system. The News sat down with Fischer to learn more about her and her work.

Q. You built up the research team known as the Yale Exoplanet Group. What exactly does your team do?

A. We are a research team that works to detect planets outside of our own solar system. We have a survey of about 600 stars at the Lick Observatory in California, a new planet survey at the Cerra Tololo Observatory in Chile and a survey of 800 stars at the Keck telescope in Hawaii. Since arriving at Yale, my team has detected several planets using the Keck telescope.

Q. How does one search for planets?

A. Our technique does not directly see the planets: Rather, we observe the “wobble” of the stars around which the planets orbit. Because their gravity pulls, however slightly, on their star, planets can subtly change the velocity of their star’s movement. If there isn’t a planet orbiting the star, its velocity will never change; it’s constant. But if there’s a planet, then that velocity increases and decreases. We map those changes out and model them mathematically to detect a planet. Given the amplitude of the planet’s pull on the star, we can actually deduce where the planet is in its orbit and how massive it is.

Q. You’ve discovered over 300 planets in your career so far. What’s your biggest goal for the future — or is it unclear?

A. I feel very clear about our top priority: We need to build better instruments to obtain more precise measurements, so that we can discover analogs of our own beautiful world — a small rocky planet ladled with oceans of water. Those instruments do not yet exist; we are going to have to think outside the box to figure out how to achieve the factor of ten improvements in our measurement precision. But if we don’t make this breakthrough, we will not be able to reach the goal of detecting Earth-like planets.

Q. Why would we want to find planets at all?

A. The reason is that we’re really interested in figuring out if there is life somewhere else in the universe. However, we think it’s unlikely that life forms on “gas giant” planets like Jupiter or Saturn: Gravity on the surface of such planets is crushingly powerful. You can’t have liquid water on such planets, either, and we think our oceans played a big role in the formation of life on Earth. We want liquid water, and we want rocky planets so that the water can pool on the surface of the planet.

Q. How likely do you think it is that there’s really an “Earth Mark II” out there?

A. I’ll bet my salary for the next year on it. It’s true that we can’t detect Earths yet, [but] we’re getting really close, and the number of planets we can see just keeps rising and rising.

Q. Are students involved with the search for exoplanets?

A. Students are very involved in the research. I have three graduate students who help collect data, carry out analysis, run theoretical simulations and analyze stellar spectra. They are also helping with the commissioning of a spectrograph that we built and commissioned at Cerra Tololo. There are also undergrads who participate in research: Nick van Nispen ’11, AJ Eldorado Riggs ’11, Joe O’Rourke ’12, Charlie Sharzer ’12, Zak Kaplan ’13 and Farris Gillman ’13 all help with the program. The students work on instrument development, they write computer code to carry out theoretical simulations, they go to the observatories to collect data and they model the data to detect planets.

Q. What makes Yale’s astronomy program so special compared to its peers?

A. I think the thing that’s special about Yale is the access we have to time on the Keck Telescope in Hawaii: being able to use the world’s largest telescope means that the quality of data we get is second almost to none. I say “almost” because we’re commissioning an instrument in Chile right now that may surpass what we’re able to do with the Keck Telescope. But I think the fact that Yale has invested real money in getting access to the Keck time and real money in helping me set up our exoplanet lab made a huge difference.