Scientists from Nasa and Japan’s Osaka University have proposed that rogue planets, which are unattached to any star and float freely through space, vastly outnumber planets circling stars.

This result suggests that Nasa’s Nancy Grace Roman Space Telescope, which is scheduled to launch in May 2027, could identify up to 400 Earth-mass rogue worlds.

According to David Bennett, a senior research scientist at NASA’s Goddard Space Flight Centre and co-author of two papers outlining these findings, “we estimate that our galaxy is home to 20 times more rogue planets than stars – trillions of worlds wandering alone.”

This is the first estimate of the number of rogue planets in the galaxy that is sensitive to planets smaller than Earth’s mass.

The team’s findings are based on a nine-year survey called Microlensing Observations in Astrophysics (MOA), which was undertaken at New Zealand’s Mount John University Observatory.

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