Orphan planets may roam the galaxy in large numbers

Monday, 23 May, 2011

There could be a sizeable number of planets drifting alone through the cosmos – that are not in orbit around a star – according to Japanese astronomers, who have identified ten such bodies that appear to be no where near a host star.

Ten objects does not sound like a lot, but microlensing events are very rare, because they require the precise alignment of a background star, the planet “lens” and Earth. So the researchers say the new observations imply that lonely planets are 50 per cent more common than planets that have host stars and nearly twice as common as stars in the galaxy.

Such planets were likely evicted from the planetary system they formed in as a result of gravitational tussles with other bodies orbiting their host star.

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