NASA's orbiting Kepler telescope has discovered an unlikely pair of planets orbiting a distant star. One is small and rocky, the other is large and gaseous. What makes them unusual is that both are orbiting close to their parent star and they routinely come very close to each other, within only 1.2 million miles.
"Here we have a pair of planets in nearby orbits but with very different densities," said astronomer Steve Kawaler of Iowa State University, one of the co-authors of the report appearing in the journal Science. "How they both got there and survived is a mystery."
Kepler is designed to detect planets circling other stars by observing variations in the stars' brightness as their planets pass between the star and Earth. Astronomers using it have so far identified 72 confirmed planets and have several hundred more possibilities. The new planetary pair was identified circling a star called Kepler-36, which is about 1,200 light-years from Earth in the constellation Cygnus. The star was already known to have one planet circling it.
A team headed by Joshua Carter of the Harvard-Smithsonian Center for Astrophysics was examining such systems looking for examples with multiple planets. Astronomer Eric Agol of the University of Wisconsin suggested that the team use a different algorithm to analyze the subtle changes in brightness that are detected by Kepler, and the Kepler-36 pair popped up immediately.
"We found this one on a quick first look," Carter said. "We're now combing through the Kepler data to try to find more."Los Angeles Times