Blurring The Lines Between Stars And Planets: Lonely Planets Offer Clues To Star Formation
Things used to be so simple. On the one hand, there were stars: gigantic incandescent nuclear furnaces, emitting substantial amounts of light. On the other hand, there were planets, with much lower masses than stars, reflecting their host stars’ light. Stars formed from the collapse of gigantic clouds of gas; planets formed in disks of gas and dust around their nascent host stars. In between there was the somewhat more ambiguous class of brown dwarfs: an intermediaries between planet and star, more massive than a planet, but with insufficient mass for nuclear fusion to ignite in the object’s core, turning it into a star. Now, two new discoveries have blurred the border between these kinds of object even further, as they show that free-floating objects with planet-like masses very likely form like stars.
Using the Pan-STARRS 1 (PS1) telescope on Hawai’i, an international team of astronomers led by Michael Liu from the University of Hawaii has discovered an exotic young object with a mass six times that of the gas giant Jupiter, which is floating in space on its own – no host star in sight. The object, dubbed PSO J318.5-22, is located just 80 light-years away from Earth, in the constellation Capricornus. Its properties are similar to those of giant gas planets found orbiting around young stars. At an estimated age of 12 million years, it is an adolescent in terms of planetary or stellar ages.