David Kipping seeks new and unexpected worlds

David Kipping, 33
Astronomer
Columbia University

By early next spring, astronomer David Kipping hopes to know if the object he’s spent his early career searching for is really there.

An astronomer at Columbia University, Kipping is perhaps most known for a project sifting through data from the Kepler space telescope on more than a thousand planets orbiting distant stars. But he’s more interested in their moons. A moon could be a home to alien life even if its planet is inhospitable (SN: 2/9/13, p. 5). A moon could also make its host planet more likely to harbor life. Some models suggest that the presence of our moon might have helped make Earth a nice place to live. The same could be true for other moon-planet partnerships.

So Kipping’s search, dubbed the Hunt for Exomoons with Kepler, gets at the fundamental nature of our place in the universe: Are we alone?

In late October, Kipping and colleagues will use the Hubble Space Telescope to find out if they’ve caught their first quarry. The possible candidate is a Neptune-sized object orbiting the planet Kepler 1625b (SN: 8/19/17, p. 15). If the candidate turns out to be a genuine exomoon — Kipping is quick to point out that similar hints have fizzled before — he will no doubt solidify his reputation as “the moon guy.”

But he dabbles in a lot of things. “I write a lot of failed papers,” he admits. He arrived at exomoons by following a simple philosophy: No idea is too crazy.

“His signature projects are quite risky, but with obvious large payback,” says Dimitar Sasselov, director of the Harvard Origins of Life Initiative, who worked with Kipping in his postdoc research at Harvard University.

Kipping, now 33, grew up in a small town in England. He loved Star Trek, wanted to be an astronaut and memorized the names and masses of all the planets in the solar system — and their moons.

Supportive teachers encouraged him to pursue a career in physics at a time when exoplanet research was just starting to be taken seriously. By 2003, when he was an undergraduate at the University of Cambridge, there were a few dozen known exoplanets. But there are 100 billion stars in the Milky Way. “It felt like there was a huge wave of discovery waiting to happen,” Kipping says.

Six years later, NASA launched Kepler and within five years, the number of known exoplanets ballooned to well over 1,000.

All the planets Kepler has picked up made themselves known by blocking their star’s light as they crossed, or transited, in front of the star. Those transits produce a characteristic U-shape in graphs of starlight over time. As a graduate student at University College London, Kipping considered what the U-shaped graphs might reveal about the planets. Researchers already knew that deeper U’s mean larger planets, for example. More frequent U’s mean shorter orbital periods.

While staring at the stars on a hiking trip in the Himalayas, Kipping thought of something else that could change the U. “It was just obvious to me that a moon could screw it up,” he says. A large enough moon would create an occasional extra dip in the light.

In the early days of the exoplanet boom, actually looking for such dips in the Kepler data was an audacious notion. But Kipping jumped in anyway. “I assumed it would be a tiny effect, but it turned out to be detectable,” Kipping says. His paper, published in Monthly Notices of the Royal Astronomical Society in 2009, pointed out that Kepler could be used to search for exomoons, too.

To pursue the search in earnest, Kipping taught himself new data processing techniques. The problem proved so computationally intensive that he turned to crowdfunding to buy a supercomputer while a postdoc at Harvard. His hunt caught on in the popular press, with write-ups in Time magazine and Wired. And other scientists joined the chase as well, with several more groups announcing competing searches in the past few years.

There’s a reason Kipping’s team has found only one exomoon candidate so far: There aren’t many out there big enough for Kepler to see, according to his statistical work. “Because he’s doing such a careful job, it probably means something,” Sasselov adds. The systems the team has checked that show no moons most likely aren’t hiding any.

As a new faculty member at Columbia, Kipping has lately turned his attention to teaching, mentoring and outreach. Many of his students say he supports their wildest pursuits — even those outside astronomy, like machine learning or linguistics.

“He’s known for out-there ideas,” says current graduate student Moiya McTier, who first worked with Kipping as an undergrad student in the Banneker Institute at Harvard, a program to prepare students of color for careers in astronomy. “Which is great, because I don’t feel afraid of going to him with my own crazy ideas.”

Kipping’s latest experiment is a YouTube channel aimed at nonscientists. “Outreach isn’t really rewarded in the academic world,” he says. “It’s a thing I wouldn’t have done as a postdoc, but felt it was a risk I was willing to take as a faculty member.”

It has paid unexpected scientific dividends already. While preparing a video about the Breakthrough Starshot initiative, which aims to send tiny spacecraft at 20 percent the speed of light to visit the nearest star to the sun (SN: 9/2/17, p. 4), Kipping realized there was an error in the Breakthrough team’s calculations of the photon pressure needed to propel the craft. The error connected back to Albert Einstein’s 1905 paper about special relativity and came from some assumptions made for simplicity that wouldn’t hold in real life.

Kipping’s paper discussing the error was published in June in the Astronomical Journal.

“I would never have written a paper about special relativity if I hadn’t been doing outreach about Starshot,” he says. His philosophy makes more sense every year: Let all the crazy in. You never know where it will lead.