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Mercury Sole Survivor of Close Orbiting Planets Around the Sun

by Nola Taylor Redd, SPACE.com Contributor   |   June 12, 2015 06

A tightly packed system of planets, named Kepler-444 and shown in this artist's representation, is the only system known to bear similarity to the solar system. Credit: Tiago Campante/Peter Devine View full size image

The vast quantity of planets and planetary candidates identified by NASA's Kepler spacecraft has revealed an array of systems. Some have Jupiter-sized planets close to the sun, while others show only a handful of planets. Almost none resemble our solar system.
In an effort to establish how the sun and its planets compare to thenewfound systems, a pair of astronomers suggest that our early solar system may have contained as many as four planets orbiting closer to the sun than Venus, and that a series of cataclysmic collisions left Mercury as the last one standing.
"One of the problems in the solar system is that, by Kepler standards, Mercury is very far from the sun," planetary scientist Kathryn Volk, of the University of British Columbia, told Astrobiology. [The Strangest Alien Planets (Gallery)]