An international team of astronomers has discovered an exotic young planet that is not orbiting a star.
This free-floating planet, dubbed PSO J318.5-22, is just 80 light-years away from Earth and has a mass only six times that of Jupiter.
The planet formed a mere 12 million years ago—a newborn in planet lifetimes.
It was identified from its faint and unique heat signature by the Pan-STARRS 1 (PS1) wide-field survey telescope on Haleakala, Maui.
Follow-up observations using other telescopes in Hawaii show that it has properties similar to those of gas-giant planets found orbiting around young stars. And yet PSO J318.5-22 is all by itself, without a host star.
"We have never before seen an object free-floating in space that that looks like this.
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| Michael Liu |
"I had often wondered if such solitary objects exist, and now we know they do."
During the past decade, extrasolar planets have been discovered at an incredible pace, with about a thousand found by indirect methods such as wobbling or dimming of their host stars induced by the planet.
However, only a handful of planets have been directly imaged, all of which are around young stars (less than 200 million years old).
PSO J318.5-22 is one of the lowest-mass free-floating objects known, perhaps the very lowest. But its most unique aspect is its similar mass, color, and energy output to directly imaged planets.
"Planets found by direct imaging are incredibly hard to study, since they are right next to their much brighter host stars. PSO J318.5-22 is not orbiting a star so it will be much easier for us to study.
It is going to provide a wonderful view into the inner workings of gas-giant planets like Jupiter shortly after their birth," said Dr. Niall Deacon of the Max Planck Institute for Astronomy in Germany and a co-author of the study.
More information: The discovery paper of PSO J318.5-22 is being published by Astrophysical Journal Letters and is available at arxiv.org/abs/1310.0457
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