A Giant Planet That's Freakishly Far From Its Sun

Canadian astronomers have discovered a gigantic planet-like object that's so far from its parent star that it takes 80,000 years to complete a single orbit — a distance that's 50 times farther than Pluto is from our sun. The discovery may force a re-think into how and where planets are capable of forming.

Called GU PSc b, it's a super-Jupiter that's 155 light-years away and about 10 times the mass of our Jupiter. It's 2,000 times farther from its star than the Earth is from the sun, or 67 times farther than Neptune. But according to the astronomers who made the discovery, the planet is bound to its star via gravity despite the extreme distance, telling the CBC that: "The planet is actually moving with its star."

A Giant Planet That's Freakishly Far From Its Sun

(Gemini Observatory)

The University of Montreal researchers surmise that the object may actually be a brown dwarf, a so-called "failed star." Regardless, it shows that planets can form farther away from stars than previously thought. What's more, the discovery indicates that some planets may not always form in the protoplanetary disk, and that we still have lots to learn about brown dwarfs (if that's indeed what it is).

More from the Gemini Observatory release:

The researchers were looking around GU Psc because the star had just been identified as a member of the young star group AB Doradus. Young stars (only 100 million years old) are prime targets for planetary detection through imaging because the planets around them are still cooling and are therefore brighter. This does not mean that planets similar to GU Psc b exist in large numbers, as noted by by Étiene Artigau, co-supervisor of Naud's thesis and astrophysicist at the Université de Montréal. "We observed more than 90 stars and found only one planet, so this is truly an astronomical oddity!"

Observing a planet does not directly allow determining its mass. Instead, researchers use theoretical models of planetary evolution to determine its characteristics. The light spectrum of GU Psc b obtained from the Gemini North Telescope in Hawaii was compared to such models to show that it has a temperature of around 800°C. Knowing the age of GU Psc due to its location in AB Doradus, the team was able to determine its mass, which is 9-13 times that of Jupiter.

This planet, which is only one of a handful to be discovered via direct imaging, obviously can't host life given its temperature, but it could host a potentially habitable moon. As noted by the researchers, however, life-bearing conditions wouldn't last long because the planet is cooling rapidly as it ages.

Read the entire scientific paper here.

Image: Lucas Granito