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Last updated at 10:53 BST, Friday, 20 May 2011

Lonely planets

Summary

20th May 2011

Japanese astronomers claim to have found 'planets' which don't go round a star.

Writing in the magazine 'Nature' they say they have found ten Jupiter-sized objects which they could not connect to any solar system.

Reporter:
Neil Bowdler

How the 'floating planet' might look

Artist's impression of one of the 'floating planets'

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Report

The researchers claim to have found ten dark gas giants floating at the heart of our Milky Way without any nearby star to illuminate them. Astronomers have long suspected such rogue planets existed, but this is the first evidence, and the Japanese team believe there could be as many out there as there are stars, a finding likely to shock many.

How they came into being is unclear. One theory is that they may be cast-outs, forgotten worlds ejected from infant solar systems by gravitational forces or interplanetary collisions.

Strictly speaking, the objects aren't even planets, as by definition planets orbit a star or the remains of one. But should the researchers have their calculations right, then strange dark orbs which look very much like planets are out there, far far from any shining star.

Neil Bowdler, BBC News

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Vocabulary

gas giants

large planets which don't have a solid surface

rogue

unconventional, not normal

came into being

were formed, created

cast-outs

objects that have been thrown away

ejected from

thrown out of

gravitational forces

the natural attraction that pulls objects in space together

interplanetary collisions

crashes between planets

Strictly speaking

Being accurate

the remains of

what is left of

orbs

round, ball-shaped objects