Far beyond our own sun lie millions of alien planets—exoplanets—which astronomers have only recently began to study. Exoplanet researcher, Professor Eliza Kempton, Physics, was recently featured in a segment on the BBC World Service’s weekly “Science in Action” segment, where she discussed the discovery of water vapor in one such planet’s atmosphere.
An article published last week in the prestigious journal Nature describes the study of the memorably named HAT-P-11b, a roughly Neptune-sized, gaseous planet located some 120 light years from Earth. The team of astronomers, who hailed from the University of Maryland, California Institute of Technology and various international universities, was the first to locate water in a planet of such a small size. Nature contacted Kempton and asked her to write a commentary on this research.
Kempton had previously written a commentary on another Nature article, and said that the point of a commentary is to write about the research and its larger meaning for a broader audience.
Photo by Jun Taek Lee.
“It’s fun to really think deeply about the implications and to share that with an audience that wouldn’t be able to digest the actual scientific paper,” Kempton said.
After the piece in Nature was published, the producers of “Science in Action” contacted Kempton and asked if she would be interested in recording an interview about the research. To ensure high-quality audio for the show, which is distributed both by broadcast and podcast, Kempton was asked to conduct the interview from a local radio station. Kempton held her conversation by phone at the Iowa Public Radio studio in Des Moines.
“It is somewhat intimidating in that you’re very much on the spot. It wasn’t a live interview, so that took some of the pressure off,” Kempton said. She guessed that her conversation was originally about 10 minutes long, but was edited into a more compact four-minute segment.
In her interview, Kempton discussed how the study was conducted. The research team sent its proposal to a NASA agency that facilitates research projects, which use the agency’s Hubble, Kepler and Spitzer Space Telescopes. The proposal was accepted and the researchers were able to use the transmission spectroscopy tools on the Hubble Space Telescope to monitor their targeted planet.
For this research, the exoplanet must pass in front of its star, a process that takes several hours. The telescope registers a decrease in light received from the star—a decrease of about a third of a percent. A very small portion of the light received has passed through the atmosphere of the planet, and this is the light that transmission spectroscopy analyzes.
“Transmission spectroscopy … [takes] advantage of the fact that different kinds of atoms and molecules absorb light at specific, characteristic wavelengths … So we know what wavelengths of light are absorbed by water vapor molecules. And what they see for this planet is that the light is absorbed exactly at that set of wavelengths,” Kempton said in her interview with the BBC.
The procedure has been used to analyze the atmosphere of larger planets, roughly the size of Jupiter, but for planets of this size, four previous analyses had all failed. According to Kempton, scientists believe this is attributable to thick clouds blocking light from passing through the atmosphere, and the apparent absence of these clouds on HAT-P-11b reassured her that smaller planets could be analyzed from afar.
In the future, Kempton will be working with several of the scientists from this study in analyzing further data from the Hubble telescope, though Kempton and her colleagues are eagerly anticipating the launch of the James Webb Space Telescope, which would provide much better tools after its scheduled launch in 2018.
Kempton has been surprised that the Hubble has been able to carry out this research—the telescope was launched in 1990, before anyone was able to study exoplanets. When Kempton joined the field in 2003, she said, there were barely 100 exoplanets known. Today, there have been over 1,000 exoplanets located, and each year they give up a few more of their secrets.
