Extreme Dwarf Planet FarFarOut Could Be the Most Distant Known Object in the Solar System

By George Dvorsky on at

Just months after discovering FarOut, the most distant known object in the Solar System, the same team of astronomers has detected the faint—but not yet confirmed—glimmerings of an object even farther away. Dubbed FarFarOut, the extreme dwarf planet is 13 billion miles away—a distance so far it takes nearly 20 hours for the Sun’s rays to reach it.

Sometimes it takes a snow day to foster an incredible scientific discovery.

Astronomer Scott Sheppard from the Carnegie Institution for Science was supposed to give a lecture last week in Washington DC about the ongoing search for hypothetical Planet Nine, reports Science Magazine. But when inclement weather forced him to postpone the event, Sheppard decided to pore over astronomical data collected by his team in January.

And that’s when he spotted it—an object located 140 astronomical units (AU) from Earth, where 1 AU is the average distance from the Earth to the Sun, a span of around 93 million miles. The newly discovered object—likely an extreme dwarf planet—was given the placeholder name FarFarOut, potentially displacing FarOut as the most distant known object in the Solar System.

Back in December 2018, Sheppard, along with colleagues Chadwick Trujillo from Northern Arizona University and David Tholen from the University of Hawaii, spotted FarOut, or 2018 VG18, a 310-mile-wide (500 km) Kuiper belt object located 120 AU from Earth. Earlier in the year, the same team discovered Goblin, or 2015 TG38, another extreme dwarf planet located at 80 AU. All objects, including FarFarOut, were detected by this team with the Japanese Subaru 8-metre telescope located atop Mauna Kea in Hawaii. Other previously known distant objects include Eris at 96 AU and Pluto at 34 AU.

An image of FarFarOut, located between the yellow crosshairs. (Image: Scott Sheppard/Carnegie Institution for Science)

This trio of astronomers has been scouring the Kuiper belt for years, conducting the largest and deepest survey ever attempted of the region. This search could lead to the discovery of the hypothetical Planet Nine, sometimes called Planet X, which is thought to exist owing to the anomalous orientation of some objects in the outer reaches of the Solar System. Planet X has yet to be found, but with each discovery of other Kuiper belt objects, astronomers are inching closer to either proving or disproving its existence.

“It’s exciting to be looking at sky that no one has ever imaged as deeply as we are,” Sheppard told Gizmodo. “To paraphrase Forrest Gump, each image we take is like a box of chocolates—you never know what you’re going to find.”

The ability to detect objects at such extreme distances depends on the size of the object, he said, and we should be able to see big objects even if they are really far away. FarFarOut is about 250 miles (400 km) long, which is near our current ability to detect objects at around 140 AU. Indeed, in the image showing FarFarOut, the object appears as a faint speck of light. Had it been any smaller, FarFarOut would have likely evaded detection, explained Sheppard. That said, if objects bigger than FarFarOut exist beyond 140 AU, we should be able to detect them.

“We have covered about 25 per cent of the sky to date in our survey, so there are likely a few bigger objects even further out than FarFarOut that we should be able to detect,” said Sheppard.

For now, the existence of this alleged extreme dwarf planet hasn’t been conclusively proven. Sheppard needs to see it again to confirm that it’s actually there, and to confirm its orbit.

“Right now we only have observed FarFarOut for a 24-hour time base,” he said. “These discovery observations show the object is around 140 AU, but it could be somewhere between 130 and 150 AU as well. We also don’t know its orbit yet since we have not made the required followup observations.”

But while a snowstorm can be credited for motivating this discovery, inclement weather would now be a major hindrance.

“I’m currently in Chile at the Magellan telescope right now and we are hoping for good weather over the next several days in order to re-observe this interesting object,” he said. [Science Magazine]

Featured image: Roberto Molar Candanosa/Carnegie Institution for Science