October 16, 2012
Astronomer Finds Most Compact Planetary System Known
Lee Rannals for redOrbit.com - Your Universe Online
Scientists have found one particular planetary system that crams five planets into a region less than one twelfth the size of the Earth's orbit.
"All five planets zip around their star within a region 150 times smaller in area than the Earth's orbit, despite containing more material than several Earths (the planets range from 1.3 to 2.6 times the size of the Earth). At this rate, you could easily pack in 10 more planets, and they would still all fit comfortably inside the Earth's orbit," Ragozzine said.
NASA's Kepler mission has helped to discover these compact planetary systems by observing over 160,000 stars simultaneously, and identifying small dips in a star's brightness. KOI-500 is the most compact planetary system found so far.
"From the architecture of this planetary system, we infer that these planets did not form at their current locations. The planets were originally more spread out and have 'migrated' into the ultra-compact configuration we see today," said Ragozzine.
Theories for the formation of the large planets of the outer solar system involve planets moving during the formation process, and it is unclear how the inner planets in solar systems like our own avoided this fate.
Astronomers can use Kepler data to measure the sizes and orbits of the planets orbiting Sun-like stars more precisely than ever before.
Planets in KOI-500's case are so close together their mutual gravity pushes and pulls on their orbits, causing slight changes in the times that the planets pass in front of their host star.
Astronomers recently confirmed that the two candidates orbiting farthest from KOI-500 were actually planets.
Ragozzine's work confirms additional planets and characterizing their masses and orbits. Ragozzine and his colleagues suggests that planetary migration helped to synchronize the planets.
"By precisely characterizing the delicate arrangement of planets in this extraordinarily crowded system, Kepler is providing insights into the formation of KOI-500 and other compact planetary systems," said Eric Ford, an associate professor of astronomy at the University of Florida and a contributor to the study.
Ragozzine said KOI-500 is the most compact system of a new compact population of planets, and it will become a touchstone for future theories that will attempt to describe how compact planetary systems form.
"Learning about these systems will inspire a new generation of theories to explain why our solar system turned out so differently," he said in a press release.