The search for habitable planets beyond our solar system has long been a subject of interest for astronomers and non-astronomers alike. But it was not until NASA launched the Kepler Mission in 2009 that there was enough data to begin seriously analyzing "super-Earths," giant planets and Earth analogs, according to Dimitar Sasselov, a professor of astronomy at Harvard University who directs Harvard's Origins of Life Initiative.
Sasselov spoke to audience members in a colloquium Wednesday afternoon sponsored by the Department of Physics and Astronomy.
Before astronomers could begin to look for and analyze Earth-like extrasolar objects, they needed to gather large quantities of accurate statistics and data, Sasselov said.
"We were woefully behind in doing our homework to find if life is on other planets, and a key part of the Kepler Mission is trying to catch up," Sasselov said.
While previous missions examining extrasolar objects were only able to view giant planets, the Kepler Mission allows astronomers to view relatively small planets with masses much closer to that of the Earth, Sasselov said.
The Kepler Mission uses the "transit method" to find information about the physical characteristics of a planet, Sasselov said.
The transit method of detecting extrasolar planets uses photometry the study of an object's electromagnetic radiation to study a planet's movement around its parent star. Scientists can contrast the levels of brightness as the planet crosses in front of its parent star and ultimately determine the relative size of the planet to star, Sasselov said.
The Kepler Mission can find transits more easily than previous telescopes because it has an extremely large field of view in comparison to other space telescopes such as the Hubble Space Telescope which dramatically increases the number of stars that Kepler can view and provides a far better chance of viewing transits, Sasselov said.
"The mission is a telescope which is specially designed to discover planets like the Earth, and the way it does that is by having a very large field of view of very good optical quality," he said.
The Kepler Mission maintains a single field of view containing over 15 million stars in order to provide astronomers with "an uninterrupted field of view to maximize our chances of finding as many planets as we could," according to Sasselov.
The Kepler Mission was originally pitched to NASA with the goal of gaining information through statistical analysis, Sasselov said.
"You start with the radius, the mass and the mean density [of planets,] and then you try to extract as much information as you can from it," Sasselov said.
The accuracy of the statistics has surpassed the expectations of most astronomers and has enabled them to engage in astroseismology, a way of studying the interior structures of planets and stars, he said.
"We didn't anticipate that the results would be good enough to do astroseismology the accuracy here is just unprecedented," Sasselov said.
Sasselov, who has been a member of the Kepler team for 10 years, said the mission has provided unprecedented levels of data that have enabled astronomers to continually refine their understanding of Earth-like objects outside of our solar system.
"[Kepler] keeps sending us data, and the longer the data stream has become, the more interesting things we have been able to find," Sasselov said.
He added that once enough information is gathered through astroseismology, astronomers can begin to determine the geochemistry of distant super-Earths, or planets that are larger than Earth but smaller than the gas giants Saturn and Jupiter. The goal is to see if they have any "biomarkers," or signs that may indicate conditions to support Earth-like life, such as active surface crust.
"Right now I'm getting a lot of parameters from Kepler for what I want to do next, which is to find the geochemistry of those super-Earths," Sasselov said.
Sasselov acknowledged, however, that there are limitations to what the Kepler Mission can accomplish.
"Kepler can drive us all the way to the point that we can start thinking about biomarkers, but I don't think we will be able to go much farther than that," Sasselov said.
