Postdoc Spotlight: Astrophysicist Sharon Xuesong Wang

DTM Postdoctoral Fellow Sharon Xuesong Wang researches planets outside our Solar System.

The seed was planted back in northeastern China.

Sharon Xuesong Wang stared stunned at the night sky practically every night growing up in her rural hometown, away from city lights. There, the Milky Way was easily visible, and it was common to see Wang with a pair of binoculars spotting the stars and planets on her sky map. After growing up loving math and learning about modern physics in college, she realized she wanted to become an astrophysicist.

Now, as a DTM Postdoctoral Fellow, Wang is still spotting planets outside our Solar System. But she is using more powerful tools than simple binoculars.

In this month's Postdoc Spotlight, Wang reflects on questions that are not too different from those her research tries to answer about our Solar System: Who is she? Where does she come from? And where is she going?

DTM Postdoctoral Fellow Sharon Xuesong Wang and Staff Scientist Paul Butler at the March for Science on April 22, 2017 in Washington D.C.

As an astrophysicist, what's your ultimate goal?

Wang: Find the closest Earth 2.0—the Earth twin—and find all nearby Earth analogs, too. I do that just out of curiosity. Are there planets just like our Earth? Where is the closest one? What are they like?

What's exciting about what you do?

Wang: I like the quote from the thesis of my thesis advisor, Jason Wright, "Of all of the topics of study in astronomy, exoplanets hold a special place in the imagination. More than stars, nebulae, or galaxies, they are places." The most exciting part to me is that we are looking for places where, far in the future, humans could potentially set their feet on.

Why is your work important?

Wang: It really addresses one of those fundamental questions that most humans are curious about: Are we alone? We are not only looking for planets like ours that maybe one day we will go to, but we are learning about other planetary systems. From that we can learn about the origin of our own Solar System.

How did you first hear about DTM? What brought you here?

Wang: I first heard about it from Jason Wright. He got the fellowship I have now when he graduated, but he didn't take it for personal reasons. Paul Butler collaborates with Jason. They both know each other from graduate school, and he visited Penn State when I was working with Jason. I took Paul to lunch and learned more about DTM. Paul is really one of the giants in our field, and my thesis was built on his work. When I visited DTM in Fall 2016, I knew this would be my dream job. I'm very lucky to work at this place with these amazing people.

What's your experience been like at DTM?

Wang: It's been fantastic. It's truly a place where I felt completely free to pursue what I'm passionate about, with minimal distractions. The support is great, the staff scientists here are great, and the lunches are amazing.

This animation shows how the gravity-driven wobble a planet induces on its star results in changes to the color of the light scientists such as Wang observe, in what is known as the radial velocity method. Image courtesy NASA JPL (full animation).

What projects are you working on now at DTM?

Wang: I'm working on improving our ability to find small, rocky planets, like our Earth. To be specific, Paul and I use the "radial velocity method" to look for planets. The gravitational pull of planets induces a wobble on its host star, and this wobble results in velocity changes along the "radial" direction, that is, along our line of sight. Such velocity changes cause the Doppler effects of light. We use this effect to find planets.

It's a tough technique, and to find Earth, we need to be sensitive to speed of 10 cm/s. That's slower than people walking. There are many hurdles to jump over, and I'm working on several specific aspects, including the contamination caused by Earth's atmosphere, data analysis techniques, and most importantly, understanding the stars themselves.

At Carnegie we use the Planet Finder Spectrograph on the Magellan II telescope at Las Campanas Observatory in Chile. This spectrograph is being upgraded right now. Paul and I will be working on analyzing the data from the upgraded telescope. Next year when the Transit Exoplanet Survey Satellite (TESS) launches, we will be busy following up exciting planets discovered by TESS.

What has been your favorite project?

Wang: Understanding the stars themselves in order to reach the precision of 10 cm/s. The velocity variation that Earth induces on our Sun is about 10 cm/s. However, the Sun itself changes all the time. Things such as its oscillation and Sunspots, which have nothing to do with the planets, could cause velocity variations. There have been several cases in exoplanets where people mistook these signals from the star as planets. I'm leading a project called RVxK2, which uses simultaneous ground-based radial velocity measurements and space photometry taken by the Kepler mission to try to understand these signals from the stars. We are kicking off our observations this December. I'm very excited about this project and what we will learn from the dataset.

What research do you hope to pursue at your next job?

Wang: I hope to work more on our understanding of a star, particularly on how to disentangle intrinsic stellar velocity variations from the variations induced by planets. I also want to spend more time on surveying the nearby stars and following up transiting planets discovered by the upcoming TESS mission to understand the population of small, rocky planets.

An artist's concept of Kepler 452b, the closest Earth analog astronomers have found so far. Image courtesy NASA Ames/JPL.

Where do you see yourself in 20 years? What's your dream job?

Wang: I hope I am leading the research in finding and characterizing Earth 2.0. I hope we would have found some by then, or at least very close ones if not an exact Earth twin! I'm optimistic. I'm also hoping to be doing more research on galaxies, black holes, and cosmology. I started off this type of work in grad school. When the Large Synoptic Survey Telescope comes online in a few years, it would be a great time to jump back in.

My dream job would be a faculty position with a mixture of teaching, research, and service. I really enjoy working with students and teaching. Also, the most important part of my "dream job" would be a very functional and friendly department with good people, much like DTM.

To you, who is the most memorable scientist you've ever met? What made that person so memorable?

Wang: I think it would be Paul Butler. It's kind of a surreal experience to have my office next to his. When I first met him, I was surprised to find what an easy-going and humble person he is (especially given that he could be such an intimidating figure physically and "astrophysically").

If you could meet one of your science icons, dead or alive, who would it be? Why?

Wang: It would be Einstein. Because...who would not want to meet Einstein? OK, I heard his English was not that great, and I don't speak German, so maybe Galileo Galilei. Wait, I think we're running into language trouble again. I don't know—I think I'm really lucky that I've met quite a lot of contemporary icons in astronomy and physics: Paul Butler, Jill Tarter, Geoff Marcy, Michel Mayor, and Chen-Ning Yang, who taught me my freshmen introduction to physics. It's pretty hard to top that. I haven't met Didier Queloz (who co-discovered the first definitive exoplanet with Mayor), so maybe him. Actually, I think it's probably Vera Rubin. I missed her presence at DTM just by a few years, and that's really a shame. She was such an amazing scientist and wonderful person. I wish I had met her in person, and I wish I had a chance to work with her at DTM.