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In Search of Planets Like Ours

Associate professor of physics David Hogg and his graduate student Dan Foreman-Mackey are fearless explorers—but don’t picture them soaring inside a space ship or riding in a bumpy moon rover. They’re more likely to be found in desk chairs, sifting through celestial data on a computer at NYU’s Center for Cosmology and Particle Physics.

photo: planet

In 2012, Foreman-Mackey came to Hogg with an interest in exoplanets, or astronomical objects that rotate around a star. Fifteen years ago, the only exoplanets we knew of were the eight orbiting the Sun in our own solar system. Researchers have since identified thousands, and Hogg’s lab is searching for more.

When the universe is the lab, scientists rely on satellites to provide a steady stream of measurements from far-off celestial bodies. Before it malfunctioned in May, NASA’s Kepler space telescope had collected 4.1 years of data on its mission to survey the stars and planets in the habitable zone of the Milky Way.

That’s the kind of large-scale data that Hogg’s lab specializes in, utilizing Kepler’s star-monitoring information to search especially for “transits”—astronomical events in which a planet appears to pass directly in front of the star, slightly obscuring it. Transits indicate that a star has planets in its orbit, and Hogg explains that they can last for mere minutes or hours, with the period between transits ranging from days to years.

To make sense of all the years of Kepler’s accumulated measurements, Hogg makes use of supercomputers in the physics department and collaborates with Courant Institute colleagues Rob Fergus and Jonathan Goodman. The software developers in his lab, who write open-source code available for use by other researchers working on exoplanets, have developed tools for identifying transits within the Kepler data.

One of the best ways we can learn about exoplanets, Hogg explains, is by measuring how our sun reflects off them. Some planets, for example, reflect back an unknown darkness, suggesting that they’re comprised of elements foreign to earth. Others seem to have “hot” and “cold” sides, with extreme differences in temperature between the two.

Stumbling upon these mysteries is Hogg’s favorite part of being an astrophysicist. He describes the universe as creative, often giving us one surprise when we were in search of another.

—Catherine Woods

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