You discovered four planets, a feat very few people have achieved. Can you explain how you did in a way that many of us can understand?
Three of the planets were found using one method, called the transit method. There are four (maybe five) methods for finding planets around other stars, and this is only one of them! It depends on geometry. Imagine that you have a planet in orbit around another star. If you're very lucky, the planet's orbit is tilted “just so,” so that it passes between Earth and its host star. You can imagine the planet casting a shadow behind it, because it's blocking some of the light of its parent star. In this case, Earth would fall in that shadow, and suddenly the star would look a little dimmer to us. And it would look dimmer by the same amount, every time the planet sweeps around the star once more.
For example, if aliens were looking at the solar system and they were aligned with us, each time Jupiter transited (crossed the face of the Sun), the Sun would look 1 percent dimmer to them. They would infer the presence of the planet, based on the dimming signal. That's how the transit method works.
You can imagine that you have to stare at stars for a really long time, hoping that you catch one! And that's what NASA's Kepler mission did. It was a big silicon eye that stared unflinchingly at a part of the sky for four years, looking for the telltale dip in any of the 180,000 stars in its field of view. That's how I found Kepler-19b, Kepler-61b and Kepler-93b. The last planet was discovered accidentally — and it orbits the same star as a transiting planet.
Mike Lemonick, who's the science writer for Time, used the word "double bank-shot" to describe the second method. If there is only one planet orbiting the star, then its transits should appear like clockwork. But the planet Kepler-19b wasn't like that — it appeared five minutes early for a year, and then five minutes late for a year, and so on. It's because another planet was tugging on it!
That's called the "transit timing variation" method. I didn't invent it! A couple of other folks, including my current faculty sponsor at the University of Washington, thought of it. But my discovery bore out their idea, six years after they published it.
At Seattle’s Bumbershoot festival this year you spoke with Bill Nye, the pop scientist often seen in a bowtie. What was the highlight?
I also really liked that I received audience questions from young women about how to navigate science. I just love that, because I finally get to be the person I needed when I was in their shoes. I'm very frank about how hard I found it, and how important it is to care for oneself. I usually quote the anthropologist Stephen Jay Gould, who said, “There are few injustices deeper than the denial of an opportunity to strive or even to hope, by a limit imposed from without, but falsely identified as lying within.”
I say that very purposefully, because high-achieving women scientists often feel they are not worthy or capable or smart enough, when in fact they are (I wasn't and am not immune to such thoughts!). They've internalized the constant background noise of our culture about who is a real scientist. I could go on and on about it, but I tried to respond briefly and emphatically to those questions. I imagined other women might eventually be listening to the program on the radio (for the show StarTalk Live).
Are there any difficulties being a woman in a scientific field that, I would imagine, is predominantly male?
Yes. This question deserves a long answer to address it with the complexity it deserves, but I will give a condensed version. At every step of the way, it is harder for women and people of color. Physics is so white that most studies about bias in our field are related to gender, so I'll confine my remarks to gender for now.
We receive less grant money for the same achievements (we have to achieve roughly twice as much as a man to be perceived as equally qualified), we are offered lower salaries with the same qualifications, we are bereft of mentors and we suffer the indignity of being told it's all in our heads, or worse. But probably the largest injustice is one that could be remedied most straightforwardly, and that has to do with childcare. I'm at the part of the so-called "pipeline" where women leak the most — the step between postdoctoral researcher (a scientist with a PhD in a temporary research job) and the bottom rung of professor.
Women are just as likely to leave science at this stage if they imagine they might “ever” want to have children, than if they have them already. Tenured male professors are three times likelier to be married with families than female tenured professors. It's foolish to imagine that young women scientists don't perceive the sacrifice that might await them if they stay. To make science supportive for women is to make childcare and parental leave available (and I'll point out that the U.S. is the only developed nation that doesn't provide some paid leave to mothers).
But as it is, on top of everything else: if you are a woman who wants to stay, you have to grapple with the fact that you're likelier to do it alone.
In a recent talk you said every star has at least one planet. What happens to that planet when the star turns in on itself and goes away?
Whew, there's a question. The answer depends upon the star you orbit, because stars die in very different ways. Our own star will puff up into a wraith-like red giant star as it's dying, and it will ultimately engulf the Earth (in 5 billion years, though. No time soon!). Our atoms will ultimately enrich the interstellar medium, perhaps eventually to be formed into new stars and planets. Carl Sagan talks about it in "The Variety of Scientific Experience," which is one of my favorite books. The eventuality of the destruction of Earth by our Sun has profound philosophical and religious implications, which he addresses much more poetically than I could.
You are a NASA Carl Sagan fellow — what does this mean exactly, and how would 11-year-old you react if you told her your adult you would be affiliated with NASA?
It means I am funded by U.S. tax dollars (your money at work!) to pursue whatever science my heart desires for three years. NASA sets aside money for four-to-five Carl Sagan fellows per year. It's one of three fellowship programs that NASA offers for early career astronomers, and it's specifically for studies of planets (in the legacy of Carl Sagan). I applied competitively for it by describing what I'd do with my time, and how I'd advance our understanding of planets, particularly those around small stars. My salary is great, and I have a generous research budget that I control — so I can travel wherever I like to talk with other scientists or attend conferences. It's a dream job.
I'm sure 11-year-old me would find that very confusing and probably scary, because I was not interested in science at all then! But I'd explain to myself that relationships with people still drive my work, and I get to try to make a difference. Also, I'd be like, "I can drive now, and also eventually you'll finish puberty."
Where do you intend to put your efforts in the next few years of your career?
This is a timely question, because I'm applying for jobs right now (I have only 11 months left of my Carl Sagan fellowship), so I've been describing my five-year plan a lot. With a friend and colleague at Harvard, I determined that planetary systems occur in two distinct modes: one very similar to the solar system (lots of planets in relatively coplanar orbits), and one very dissimilar. And it's about 50/50!
I've been titling talks "Choose Your Own Adventure" lately, when I'm speaking about it. It has important implications for habitability of other worlds, because the solar-system-type arrangements are more stable in a number of ways. And I uncovered tantalizing evidence for which stellar properties are predictive of the final planetary architecture.
In the next 10 years, we'll be trying to uncover the signatures of molecules in the atmospheres of other cool, rocky planets. But even in the best of cases, it'll take five years of a dedicated campaign with the fanciest spacecraft ever built (the James Webb Space Telescope, to be launched in 2018) to start seeing the signatures of water and carbon dioxide emerge for each planet.
So it's a question of risk assessment — you want to set yourself up for success as much as possible, and pick your words very carefully. If we can determine important things about the planet because of what we can measure beforehand about the star, that would be great! I'm really trying to investigate that.