Astronomers discover solar system’s most distant object, nicknamed ‘FarFarOut’

For most people, snow days aren’t very productive. Some people, though, use the time to discover the most distant object in the solar system.



That’s what Scott Sheppard, an astronomer at the Carnegie Institution for Science in Washington, D.C., did this week when a snow squall shut down the city. A glitzy public talk he was due to deliver was delayed, so he hunkered down and did what he does best: sifted through telescopic views of the solar system’s fringes that his team had taken last month during their search for a hypothesized ninth giant planet.



That’s when he saw it, a faint object at a distance 140 times farther from the sun than Earth—the farthest solar system object yet known, some 3.5 times more distant than Pluto. The object, if confirmed, would break his team’s own discovery, announced in December 2018, of a dwarf planet 120 times farther out than Earth, which they nicknamed “Farout.” For now, they are jokingly calling the new object “FarFarOut.” “This is hot off the presses,” he said during his rescheduled talk on 21 February.

For the better part of a decade, Sheppard and his collaborators—Chad Trujillo at Northern Arizona University in Flagstaff and Dave Tholen at the University of Hawaii in Honolulu—have methodically scoured the night sky with some of the world’s most powerful and wide-angled telescopes. Their insistent search has netted four-fifths of the objects known past 9 billion kilometers from the sun.



This is not stamp collecting. Clustering in the orbits of these objects can serve as indicators of Planet Nine’s influence. Like Farout, FarFarOut’s orbit is not yet known; until it is, it’s uncertain whether it will stay far enough away from the rest of the solar system to be free of the giant planets’ gravitational tug. If it does, the two could join another of Sheppard’s recent distant discoveries, “the Goblin,” which dovetails with projections of the Planet Nine’s possible orbit.



It will take several years to determine the orbits of Farout and FarFarOut, and whether they will provide more clues. Meanwhile, with nearly every new moon, Sheppard is back out searching on his preferred telescopes, the Blanco 4-meter in Chile and the Subaru 8-meter in Hawaii. He flies to Chile next week, and Hawaii the week after.