Early Wednesday, astronomers at the University of Hawaii at Manoa reported that they found a young planet floating through the void of space without a star to call its own. The planet, dubbed PSO J318.5-22, is estimated to be about 12 million years old, making it much younger than our planet Earth.
The planet was discovered thanks to its faint heat signature, by the Pan-STARRS 1, a wide-field survey telescope located on the island of Maui. The light emanating from PSO J318.5-22 is 100 billion times more faint than the light emanating from Venus. Astronomers noticed the planet while examining data on brown dwarfs collected by Pan-STARRS, and saw that the rogue planet glowed much brighter than the dwarfs.
Before the discovery of this planet — which is located eighty light years from Earth — astronomers had not yet seen a planet with a similar age and mass traveling through space alone, not tethered to a star. Planets traveling without a star have been seen in the past, but it was never clear whether or not they were a failed star, or planet without a sun.
There is a bit of a discrepancy regarding what to call the planet, as some astronomers demand that the definition of “planet” be considered a mass that is tethered to a sun. So, if the planet isn’t orbiting a star, then technically it isn’t a planet, and rather, a planetary-mass object.
The discovery of the planet — rather than filling our heads with the dream of it actually being an enormous space ship disguised as a planet — will allow us to better study how gas giants work in their early years, as this star is an infant in the eyes of the universe.