NASA's Kepler Spacecraft Discovers Planets Locked in Surprisingly Close Orbits
Posted on June 25, 2012
Two planets discovered by NASA's Kepler spacecraft are orbiting surprisingly close to each other. The image shows how one of the planets might look from the surface of the neighboring planet. Astronomers say the planets are also locked in surprisingly close orbits around their host star. This differs greatly from the planetary pattern of our solar system: rocky planets orbiting close to the sun and gas giants orbiting farther away.
The Kepler-36 planetary system is located about 1,200 light years from Earth. It has two known planets. One planet is a rocky super-Earth about 1.5 times the size of our planet and 4.5 times the mass. The other is a Neptune-like gaseous planet 3.7 times the size of Earth and eight times the mass. The planets approach each other 30 times closer than any pair of planets in our solar system.
Steve Kawaler, an Iowa State University professor of physics and astronomy, says, "Small, rocky planets should form in the hot part of the solar system, close to their host star - like Mercury, Venus and Earth in our Solar System. Bigger, less dense planets - Jupiter, Uranus - can only form farther away from their host, where it is cool enough for volatile material like water ice, and methane ice to collect. In some cases, these large planets can migrate close in after they form, during the last stages of planet formation, but in so doing they should eject or destroy the low-mass inner planets. Here, we have a pair of planets in nearby orbits but with very different densities. How they both got there and survived is a mystery."
The research was published here in Science magazine. Lead authors of the study are Joshua Carter, a Hubble Fellow at the Harvard-Smithsonian Center for Astrophysics, and Eric Agol, an associate professor of astronomy at the University of Washington.