According to a news release from the Institute for Astronomy at the University of Hawaii at Manoa, astronomers have found a young planet that is not circling a star. This lonely planet, named PSO J318.5-22, is a mere 80 light-years away from our planet and has a mass only six times that of Jupiter. The planet developed approximately 12 million years ago.
It was spotted from its faint and uncommon heat signature by the Pan-STARRS 1 wide-field survey telescope on Haleakala, Maui. Other telescopes reveal that it has characteristics similar to those of gas-giant planets discovered circling around young stars.
"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 Dr. 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."
Over the last ten years, extrasolar planets have been found at a rapid pace, with approximately a thousand discovered by roundabout techniques like wobbling or dimming of their host stars brought about by the planet. However, only a few planets have been directly imaged, all of which are around young stars. According to astronomers, PSO J318.5-22 is one of the lowest-mass lonesome objects known.
"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.
The planet was found during a quest for brown dwarfs. Based on their seemingly cool temperatures, brown dwarfs are extremely faint and have very red colors. To work around these issues, the astronomers have been examining the data collected by the PS1 telescope. PS1 is looking at the sky every night with a camera perceptive enough to identify the faint heat signatures of brown dwarfs.
"We often describe looking for rare celestial objects as akin to searching for a needle in a haystack. So we decided to search the biggest haystack that exists in astronomy, the dataset from PS1," said Dr. Eugene Magnier of the Institute for Astronomy at the University of Hawaii at Manoa.
PS1 generates the equivalent of 60,000 iPhone images every night. The complete dataset to date is approximately 4,000 Terabytes.
Using several telescopes, the astronomers examined the PS1 finding. Infrared spectra gathered with the NASA Infrared Telescope Facility and the Gemini North Telescope revealed that PSO J318.5-22 was not a brown dwarf, due to signatures in its infrared light that are best explained by it being young and low-mass.
Based on the planet's distance from Earth and its movement through space, the astronomers determined that PSO J318.5-22 is a part of an assemblage of young stars known as the Beta Pictoris moving group that developed approximately 12 million years ago.
The study's findings are described in greater detail in the Astrophysical Journal Letters.