Five-year study will observe, catalog 150,000 Stars Looking for Earth-size Planets

VILLANOVA, Pa., November 4, 2010 -- The search for Earth-size planets that could be suitable for life is the focus of research a Villanova University astrophysicist is conducting as part of the National Aviation and Space Administration’s (NASA) Kepler Mission.

Andrej Prsa, an assistant professor in Villanova’s department of astronomy and astrophysics, is one of the science collaborators on the project that will continuously observe more than 150,000 stars over the next five years looking for planets comparable in size to our own that orbit in the habitable zone of their host stars.  A habitable zone is the distance from a host star where a planet can maintain liquid water on its surface and thereby sustain life.

The discovery of Earth-size planets with habitable zones does not guarantee that they actually feature liquid water on the surface like the planet Mars. Neither does the existence of liquid water on the surface of a planet automatically signal the presence of life, Prsa said.

But, he added, the ultimate goal of the project is to observe as many Earth-size planets in the habitable zone to try to answer the question, “How probable is life elsewhere in the universe?”

This summer the Kepler team announced a breakthrough discovery of over 700 planet candidates in the first 45 days of observations, most of which have radii smaller than Jupiter. The total number of all extra-solar planets discovered to date in the field of astronomy is less than 500. Kepler scientists are running a battery of tests on each candidate to confirm its planetary nature and determine its size and mass.

As chair of the Kepler Mission’s Eclipsing Binary Working Group, Prsa tracks and catalogs eclipsing binary stars, systems of two stars that orbit a common mass obscuring each other similar to the manner in which planets transit their host stars.   Prsa’s research group applied an artificial intelligence-based approach to all Kepler eclipsing binaries to derive fundamental properties like temperatures, radii and orbits, of companion stars. The group’s Catalog of Eclipsing Binary Stars has been one of the most popular binary star papers on astrophysics in recent months.

According to Prsa, many of the 150,000 stars being observed in the course of the project are of great interest from an astrophysical perspective even if they don’t harbor planets.

“For those, Kepler will provide us with data of unprecedented quality. The only ready way to measure the radii, masses and other physical properties of stars is to carefully model eclipsing binary components,” Prsa said. “Moreover, the methods applied to analyze eclipsing binary stars are well suited for planet transits as well, since planets can be regarded as small eclipsing components in a binary system.”

“Kepler discovered nearly 2,000 eclipsing binaries, providing us with remarkable science opportunities. Variable stars, brown dwarfs, chromospherically active (spotted) stars, cluster members, are other targets for fundamental science being done with Kepler data,” he added.

Prsa’s research group continues to data mine Kepler eclipsing binary statistics looking for evidence of tertiary components. Early results have netted a surprising find – tell-tale signatures for stellar third bodies are found in roughly one-third of the sample – an indicator that stellar multiplicity is very common. As more Kepler data are acquired Prsa’s scientific group expects to be able to detect planets around binaries. Prsa and his colleagues will present their preliminary findings at the American Astronomical Society Symposium in Seattle this upcoming January.

Answering the tantalizing question of whether we are alone in the universe will remain an open question for now, Prsa said.

“As of right now, our current capabilities are limited to searching for planets that may harbor life that depends on liquid water. To claim that these planets could sustain humanlike life or any particular form of life would be a stretch as we cannot scientifically observe that.”