WASHINGTON – Astronomers said Wednesday they have found a lonely planet outside the solar system floating alone in space and not orbiting a star.
The gaseous exoplanet, PSO J318.5-22, is just 80 light-years from Earth and has a mass six times Jupiter. Having formed 12 million years ago, it is deemed a newborn among its peers.
“We have never before seen an object free-floating in space that looks like this. It has all the characteristics of young planets found around other stars, but it is drifting out there all alone,” said team leader Michael Liu, of the Institute for Astronomy at the University of Hawaii at Manoa. “I had often wondered if such solitary objects exist, and now we know they do.”
The researchers, whose study was published in the Astrophysical Journal Letters, identified the planet from its faint and unique heat signature using the Pan-STARRS 1 wide-field survey telescope on Maui’s Haleakala volcano.
They suggested the new planet may have the lowest mass of all known freely floating objects. Other telescopes in Hawaii showed it has similar properties to gas giants orbiting young stars.
Researchers have found about a thousand extrasolar planets via indirect methods, including planet-induced wobbling or dimming of host stars. But only a handful have been observed directly, since most are orbiting young stars less than 200 million years old and thus very bright.
PSO J318.5-22 “is going to provide a wonderful view into the inner workings of gas giant planets like Jupiter shortly after their birth,” said co-author Niall Deacon of the Max Planck Institute for Astronomy in Germany.