Whether or not there is an undiscovered planet lurking in the farthest reaches of the Solar System, the search for unknown dwarf planets and other objects continues. Extreme Trans-Neptunian objects (ETNOs) are of particular interest. The closest they come to the Sun is well beyond the orbit of Neptune, with the result that they have little gravitational interaction with the giant planets. Consider them as gravitational probes of what lies beyond the Kuiper Belt.
Among the population of ETNOs are the most distant subclass, known as Inner Oort Cloud objects (IOCs), of which we now have three. Added to Sedna and 2012 VP113 comes 2015 TG387, discovered by Scott Sheppard (Carnegie Institution for Science), Chad Trujillo (Northern Arizona University) and David Tholen (University of Hawaiʻi). The object was first observed in 2015, leading to several years of follow-up observations necessary to obtain a good orbital fit.
For 2015 TG387 is a challenging catch, discovered at about 80 AU from the Sun but normally at far greater distance:
“We think there could be thousands of small bodies like 2015 TG387 out on the Solar System’s fringes, but their distance makes finding them very difficult,” Tholen said. “Currently we would only detect ...