An international team of astronomers have accidentally found a ‘never before seen’ planet ‘floating’ without orbiting a star, some 80 light years away from earth. It is a mere 12 million years old, a newborn in space terms.
“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 Michael Liu, research team leader at the
Institute for Astronomy at the University of Hawaii at Manoa.
The planet, now known as PSO J318.5-22 has a mass roughly six times that of Jupiter and was formed only 12 million years ago. While that sounds ancient, in planetary terms it is considered a mere infant.
“I had often wondered if such solitary objects exist, and now we know they do,” Liu said.
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.
Hundreds of extrasolar planets have been discovered since the mid-1990s. However, they are usually detected through indirect methods that rely on them orbiting a sun – the techniques measure a drop in the transmission of light as a planet passes in front of its star. Only a handful of them were directly imaged.
However, this ‘lonely planet’ was accidently mapped as the team
searched for brown dwarfs – a type of ‘sub-stellar’ object which
emits a faint orangey-red glow to the human eye. The team was
using the Pan-STARRS 1 wide-field survey telescope located on the
Haleakala volcano of Hawaii’s Maui island.
The study was published in the Astrophysical Journal Letters. Observations showed that while the planet indeed has similar attributes to that of a gas giant orbiting a star, it lacked its own. It further confirmed that it was not a brown dwarf, but a young planet, which will greatly benefit those seeking to observe it; as most planets with the same properties orbit young stars (less than 200 million years old) which tend to be extremely bright.
Its most unique aspect is its similar mass, color, and energy output to directly imaged planets, the press release on the university’s website says.
“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,” Niall Deacon of the Max Planck Institute for Astronomy in Germany, and a co-author of the study, said.