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Rare, free-floating exoplanet found

This artist's impression shows the solitary exoplanet PSO J318.5-22, which sits 80 light-years from Earth in the direction of the constellation Capricornus.

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A rare, rogue exoplanet without a parent star drifts through space just 80 light-years from Earth, astronomers say. The object may be the lowest-mass free-floating planet found to date in the solar neighborhood.

The exoplanet, called PSO J318.5-22, is roughly six times the mass of Jupiter and about 12 million years old, relatively young in cosmic age. It has a surface temperature of about 1,100 Kelvin and does not appear to have methane in its atmosphere, which makes it different from other free-floating objects astronomers have identified. Scientists describe the planet in a paper accepted for publication in Astrophysical Journal Letters.

Astronomers discovered PSO J318.5-22 using the Pan-STARRS 1 telescope in Hawaii. Further analysis revealed that the object is similar to other directly imaged exoplanets, including HR 8799 b, c, d and e.

The observations reaffirmed that planets with similar ages and temperatures can have different amounts of metals and other chemical compounds in their atmospheres.

Those differences could reveal whether a free-floater formed in a collapsing gas cloud by itself or formed with stars and other planets and was later ejected from the group.


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