Julien de Wit is a Postdoctoral Associate working in the Seager Group. As Julien puts it, his primary interest and expertise lies, “in the field of data science where math and science are brought together to make sense of newly accessible pieces of reality!”
Over the past five years, first as a precocious graduate student, and subsequently as an equally precocious postdoctoral associate, de Wit has dazzled, developing and applying new analysis techniques to map exoplanet atmospheres, elaborating a technique to constrain the atmospheric properties and mass of exoplanets solely from their transmission spectra, exploring the radiative and tidal planet-star interactions in eccentric planetary systems, and, most recently, as part of the team which first identified three potentially habitable planets just 40 light years away, at the time, closer and more promising than any previous targets in the search for extraterrestrial life—and culminating in a double transit observation demonstrating that at least two of these nearby planets are likely rocky.
It’s a sunny summer day as we sit looking across the Charles at Boston’s iconic skyline. At his suggestion, we have arranged to meet at MIT’s Sailing Pavilion—a place where, de Wit confides, he likes to come to dip his feet in the water when he needs a break. His excitement about his research is palpable and it should be: he’s on an enviable roll with a string of papers in big-name journals collecting on his publications page.
De Wit grew up in Belgium and came to MIT in 2008 to study for a PhD with Sara Seager. His first breakthrough came in 2013 as a member of the team which generated the first map of clouds on an exoplanet.
“The idea that we could map clouds on an exoplanet may have seemed totally audacious but it was simply part of the natural transition from discovery to characterization that has occurred in the field of exoplanetary research over the past few years,” de Wit says. “By mapping the cloud coverage on an exoplanet we can then start to understand its whole climate.”
De Wit’s second breakthrough came with the paper he wrote with PhD advisor Sara Seager, “Constraining Exoplanet Mass from Transmission Spectroscopy,” which was published in the journal Science in 2014, and demonstrated how it is possible to determine the mass of certain exoplanets based on the properties of their atmospheres.
After a lull during which time de Wit defended his doctoral thesis, “Maps and Masses of Transiting Exoplanets: Towards New Insights Into Atmospheric and Interior Properties of Planets,” he has had a flood of near back-to-back papers, first with “A Map of the Large Day-Night Temperature Gradient of a Super-Earth Exoplanet,” in the journal Nature, which was closely followed by a paper in the Astrophysical Journal, “Direct Measure of Radiative and Dynamical properties of an Exoplanet Atmosphere,” reporting observations of an extreme-weather planet raising questions about the origin of hot Jupiters. These publications were followed this May by another paper in the journal Nature, “Temperate Earth-sized Planets Transiting a Nearby Ultracool Dwarf Star,” reporting the extraordinary discovery of three exoplanets orbiting the nearby ultracool dwarf star, 2MASSJ23062928-0502285—now known as TRAPPIST-1. Ultracool dwarfs are a type of star typically much cooler than the sun, emitting radiation in the infrared rather than the visible spectrum.
Colleagues from de Wit’s alma mater, the University of Liège, came up with the idea to look for planets around such stars, as they are much fainter than typical stars and their starlight would not overpower the signal from planets themselves. Together with de Wit, the same group is now working to establish more tele- scopes on the ground to probe this planetary system further, as well as to discover other similar systems.
The researchers discovered the TRAPPIST-1 planetary system using TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope), which is a new kind of ground telescope designed to survey the sky in infrared. TRAPPIST was built as a 60-centimeter prototype to monitor the 70 brightest dwarf stars in the southern sky. Now, the researchers have formed a consortium, called SPECULOOS (Search for habitable Planets Eclipsing ULtra-cOOl Stars), and are building four larger versions of the telescope in Chile to focus on the brightest ultracool dwarf stars in the skies over the southern hemisphere. The researchers are also trying to raise money to build additional telescopes to survey the northern sky.
TRAPPIST’s efficient, turnkey design means new sites can be developed incredibly economically, and they can up and running in mere months. “Each telescope is just $400,000—less than the price of an apartment in Cambridge,” says de Wit.
If the scientists can train more TRAPPIST-like telescopes on the skies, the telescopes may serve as relatively affordable “prescreening tools,” de Wit says. Scientists can use them to identify candidate planets which just might be habitable to then be followed up with more detailed observations using powerful telescopes such as Hubble and NASA’s new James Webb Telescope, scheduled to launch in October 2018.
“With more observations using Hubble, and further down the road with James Webb, we can know not only what kind of atmosphere planets like TRAPPIST-1 have, but also what is within these atmospheres,” according to de Wit, “and that’s very exciting.”
Read more about the research: http://bit.ly/habitable-worlds
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