Undergraduate Research Exhibited on Capitol Hill
Research revealing the peculiar characteristics of a gaseous giant planet circling the distant star Kepler 2 was part of the April 24 Posters on the Hill exhibit on Capitol Hill, sponsored by the Council on Undergraduate Research. The research, by Rensselaer physics and astronomy student Emily DeLarme, was one of 60 projects selected for the honor out of a pool of more than 800 proposals.
DeLarme, working with Jon Morse, professor of physics and associate vice president for research for physical sciences and engineering, is studying data gathered by NASA’s Kepler space telescope. Kepler, launched in 2009 to search for Earth-size planets, gathers data on approximately 150,000 stars. Analysis of Kepler data has led to identification of 2,740 planetary candidates, and 115 confirmed planets.
DeLarme has been studying data generated on two of the planets—Kepler 2b and Kepler 13b—which orbit stars Kepler 2 and Kepler 13, respectively. In particular, she is looking at light during the period when the planets circle behind their stars, a phase known as the “secondary eclipse,” or “secondary transit.”
Kepler records light from the planet plus its parent star throughout the orbit, Morse explained. More than 99 percent of the light comes from the parent star, with only a small fraction reflected from the planet. The “exquisite stability” of Kepler makes it possible to see tiny dips in the total brightness caused either as the planet blocks light as it passes in front of the star—known as the primary transit—or as light reflected from the planet surface is lost during the planet’s path behind the star during the secondary transit.
Morse said the characteristics of the primary transit indicate the size of the planet and its orbital distance from the parent star. The secondary eclipse can reveal properties of the planet, as well as gravitational effects that distort the star’s atmosphere for planets with very close orbits, such as Kepler 2b and Kepler 13b. Even more tantalizing, he added, is the prospect of measuring properties of the planet’s atmosphere during different positions in the orbit.
“If you can measure the light, or even the ‘spectrum,’ of the planet you can learn a lot about the atmosphere, the reflectivity, the temperature—a lot about the properties of a planet,” said DeLarme.
Her most interesting finding thus far relates to planet Kepler 2b, a gaseous giant about one and a half times the size of Jupiter circling Kepler 2 in a tight and fast orbit (only 1.7 days). DeLarme has used the latest brightness data in the Kepler mission database to measure details of the secondary eclipse, which causes a dip in the total light of only 70 parts-per-million.
“Now that I’ve found the asymmetry, we’re trying to figure out if it’s real and why it’s there,” DeLarme said.
“I like the entire idea of figuring things out about planets that we can’t actually see, but we know that they’re there,” DeLarme said. “This is a field that’s growing a lot and it’s fascinating to be a part of this early research.”