However, Sheppard stresses that FarOut doesn’t serve as evidence for Planet Nine just yet. Because FarOut is so, well, far out, it’s very difficult to pin down its orbit. This makes it tough to tell whether the new find is actually a member of the unique group of TNOs that hint at the existence of Planet Nine, or if it’s just a run-of-the-mill object in a relatively boring, albeit distant, orbit.

Although Sheppard and his team are already pretty confident about FarOut’s speed (and therefore its distance), in order to confirm FarOut’s orbital path, they must first collect more images of it moving through the sky. “You need a year-long arc on it to actually get the orbit down,” Sheppard says. And because they don’t have a year’s worth of data for FarOut yet, he says, “we need another observation in November [2019] to actually get a reliable orbit.” At the time of this writing, Sheppard is eagerly awaiting the new November data.

But FarOut isn’t the only world that might help point the way to Planet Nine. In October 2018, the researchers announced the confirmation of another distant discovery called 2015 TG387, which, in the spirit of Halloween, they nicknamed The Goblin. Though the 200-mile-wide (320 km) icy rock was first seen about 80 AU away, it has a particularly eccentric orbit, which means it swings exceptionally far from the Sun. “The Goblin’s orbit is very large. It has a semimajor axis of some 1,000 AU,” Sheppard says, “meaning it takes some 40,000 years to go around the Sun once."

Because of the time it takes The Goblin to complete a single orbit, the team required three years of observations after its initial discovery in 2015 to determine its exact path through the sky. But once they pinned it down, they learned the eccentric TNO comes to perihelion at nearly the same point in space as a handful of other noteworthy objects. These include the team’s earlier discovery of 2012 VP113 (which they nicknamed Biden as a nod to the “VP” in its designation) and Sedna, a dwarf planet roughly half the diameter of Pluto that was discovered in 2003.

It’s this recently identified pack of perihelion-clustered objects, which Sheppard refers to as “extreme TNOs,” that suggests an unseen and massive planet is hiding in the outskirts of our solar system.

The hunt for Planet Nine

With the advancement of powerful survey telescopes, as well as sophisticated software that can sift through massive amounts of data like never before, we are just now beginning to scour the distant reaches of the solar system for icy dwarf planets and the like. But the discovery of this peculiar class of extreme TNOs indicates that dwarf planets may not be the kings and queens of the Kuiper Belt. Instead, there’s a growing dossier of evidence that suggests a colossal world some five to 15 times the mass of our own planet is lurking far beyond, playing puppeteer to the oddly clustered collection of distant bodies.