Fewer big rogue planets roam the galaxy, recount shows | Science News

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Fewer big rogue planets roam the galaxy, recount shows

New estimate of wandering Jupiter-mass worlds better matches ideas of how planets become orphans

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11:00am, July 24, 2017
microlensing illustration

QUICK FLASH  The light from a distant star may temporarily brighten when a free-floating planet passes in front of the star. This artist’s illustration shows how a rogue planet’s gravity distorts and focuses distant starlight as a ring around the planet.

Big, rogue planets — ones without parent stars — are rare.

A new census of free-floating Jupiter-mass planets determined that these worlds are a tenth as common as previous estimates suggested. The results appear online July 24 in Nature.

Planets can go rogue in two ways: They can get kicked out of their parent planetary systems or form when a ball of gas and dust collapses (SN: 4/4/15, p. 22).

In the new study, Przemek Mróz of the Astronomical Observatory of the University of Warsaw and colleagues estimated the number of large, rogue planets in our galaxy using a technique called microlensing. When an object with a mass of a planet passes in front of a distant, background star, the gravity of the planet acts as a gravitational magnifying glass. It distorts and focuses the light,

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