Guide to a Lonely Planet

It Orbits No Star, Yet Exists in Space

There’s a lonely planet out there floating in space, no host star in sight. Now, how did THAT happen? Astronomers using the Pan-STARRS-1 survey telescope on Haleakala (Maui), found this newborn planet (only 12 million years old!) in interstellar space some 80 light-years from Earth.

Nobody’s ever seen something like this before, but there it is. Astronomers found it while searching for brown dwarfs (objects to hot to be planets and too cool to be stars). The planet, called PSO J318.5-22 popped up, looking redder than any red brown dwarf so far found.  Follow-up observations using other telescopes in Hawai’i 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.

So, how does a planet get away from its star? There’s no explanation for this one yet, but we can speculate. Perhaps this gas-giant-type world was ejected from its original planetary system by its star.

Perhaps it was on the very outskirts of a stellar system and was pulled away by the gravitational pull of a passing star. Maybe it was part of a binary star system’s planets, and the gravitational dance of the two stars gave it a push out to space.

Starbirth is a very active process, so perhaps something happened as this planet and its siblings were forming, and it somehow got knocked out to space. It’s a very young star after all, and now that it has been pushed from the  nest, it’s fate is to wander interstellar space forever.Read more about this discovery here: http://www.ifa.hawaii.edu/info/press-releases/LonelyPlanet/