If celestial bodies could embrace cultural titles, then the wandering planet named PSO-J318.5-22 would be the hipster of all hipsters. Recently discovered by a collaboration of astronomers working at the Institute for Astronomy at the University of Hawaii at Manoa, the planet — which I will endearingly bestow the nickname, PJ — is perhaps the boldest example yet of Tolkien’s “Not all those who wander are lost.”
PJ uniquely stands (or floats) throughout our cosmos as the first ever discovered free-moving planetary body. In other words, it does not orbit a star, nor anything for that matter, preferring to carve its own path through the gargantuan abyss we call our universe.
It is also not terribly far from Earth, relatively at least. PJ is estimated to roam only about 80 light years away from our prying eyes. To give some context, the closest star to our sun is Alpha Centauri (which is actually a system of three stars if you cared to know) that resides about 4.3 light years away.
PJ was discovered by the Pan-STARRS1 (PS1) wide-field survey telescope located on Haleakala, Maui. This anomalous planet possesses many characteristics that liken it to a planet similar to a gas giant such as Jupiter. Gas giants share several common qualities, namely a deep atmosphere, low density, which gives it a smaller gravitational pull, and multiple satellites, or moons. The team leader, astronomer Michael Liu, a professor of astronomy at the University of Hawaii at Manoa was heading a project searching for brown dwarfs. In terms of size, brown dwarfs are objects in space that fall on the spectrum between plants and stars. They begin in much the same way as stars, as a fog of gas and dust that implodes upon itself.
However, something goes wrong during this step and the cloud fails to form the dense core that triggers nuclear fusion in the center of a healthy star. The lack of this energetic core robs the potential star from the characteristic light release we observe in say, the sun, and the collapsed mass is forever left to reside as a dim brown dwarf.
Because brown dwarfs give off relatively little heat, Liu and his team were sweeping the night sky with the PS1 survey telescope, which contains equipment sensitive enough for detecting brown dwarfs.
The team noticed sometime strange in the data: a faint red glow, redder than even the most red of the brown dwarfs that caught their attention. They’ve been tracking and studying PJ over the past couple of years.
PJ was found among a cluster, although not orbiting, of stars known as Beta Pictoris, which is dated at about 12 million years old.
In comparison, current estimates place planet Earth at roughly 4.5 billion years old. PJ was formed among and at the same time as Beta Pictoris. That makes this planet incredibly young in the framework of extraterrestrial lifetimes. It is also undeniably light (in terms of mass) per unit volume. Scientists speculate that it may perhaps be one of the very lowest-mass free-floating space objects documented.
It was previously believed that such free-floating objects were non-existent in space, although researchers in the field had some speculations. Astronomers will now be more attuned to the characteristic glow of other PJ like planets. Until then, PJ will remain quite the explorer.
