Free-floating ‘rogue’ planets the size of our Earth are everywhere in our galaxy


Free-floating ‘rogue’ planets the size of our Earth wander freely through space in our galaxy – and could, perhaps, even host life.

A new study by a team of University of Warsaw researchers investigated the number of these ‘rogues’, using a technique called gravitational micro-lensing.

The researchers used Poland’s Optical Gravitational Lensing Experiment (OGLE), a 1.3-meter telescope in Chile.

The researchers found that large, Jupiter-size planets could be less common than previously believed – with just a tenth of the number expected.

But smaller, Earth-sized worlds, hurled out of their solar systems into interstellar space, could be much more common.

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Previous research by University of Aberdeen researcher Sean McMahon suggested that such planets might harbour life beneath the surface.

‘Basically, it is much easier to eject an Earth-mass planet than a Jupiter-mass planet,’ said researcher Przemek Mróz of the University of Warsaw.

Mroz, a PHD student, said: ‘We detected a few possible ultrashort-timescale events, less than half a day, which may indicate the existence of Earth-mass and super-Earth-mass free-floating planets, as predicted by planet-formation theories.

‘The shortest-timescale events are not well covered by observations and it’s difficult, if not impossible, to either prove or disprove their nature as free-floating planets.

‘The detection efficiency at these timescales is very low, meaning a very few detections imply the existence of a large population of Earth-mass free-floating or wide-orbit planets.

‘Future space-based missions like WFIRST and Euclid will enable the exploration of these short events in more detail.’

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