Astronomers have discovered a distant body that’s more than 100 times farther from the Sun than Earth is. Its provisional designation is 2018 VG18, but they’ve nicknamed the planet “Farout.” Farout is the most distant body ever observed in our Solar System, at 120 astronomical units (AU) away.

The International Astronomical Union’s Minor Planet Center announced Farout’s discovery on Monday, December 17th, 2018. This newly-discovered object is the result of a team of astronomers’ search for the elusive “Planet X” or “Planet 9,” a ninth major planet thought to exist at the furthest reaches of our Solar System, where its mass would shape the orbit of distant planets like Farout. The team hasn’t determined 2018 VG18’s orbit, so they don’t know if its orbit shows signs of influence from Planet X.

A trio of astronomers made the discovery: Carnegie Science Institute’s Scott S. Sheppard, the University of Hawaii’s David Tholen, and Northern Arizona University’s Chad Trujillo. Members of the same team also discovered “The Goblin” in October, 2018. The Goblin is another distant world whose orbit is thought to be shaped by the elusive Planet 9.

“2018 VG18 is much more distant and slower moving than any other observed Solar System object, so it will take a few years to fully determine its orbit.” – Scott Sheppard, Carnegie Science Institute.

“2018 VG18 is much more distant and slower moving than any other observed Solar System object, so it will take a few years to fully determine its orbit,” said Sheppard. “But it was found in a similar location on the sky to the other known extreme Solar System objects, suggesting it might have the same type of orbit that most of them do. The orbital similarities shown by many of the known small, distant Solar System bodies was the catalyst for our original assertion that there is a distant, massive planet at several hundred AU shepherding these smaller objects.”

Farout was discovered with the Magellan telescope at Carnegie’s Las Campanas Observatory in Chile, and with the Japanese Subaru 8-meter telescope located atop Mauna Kea in Hawaii. The Subaru was the first to spot it, on the night of November 10, 2018.

In early December, the Magellan telescope spotted 2018 VG18 for the second time. The astronomers used Magellan for a week to confirm the planet’s path across the sky and to obtain its basic physical properties, such as brightness and color. Observations made with the Magellan telescope confirmed the distance of 120 AU. They also suggest that the planet is roughly spherical and is about 500km in diameter. The new planet has a pinkish hue, which is a color associated with ice-rich objects.

“All that we currently know about 2018 VG18 is its extreme distance from the Sun, its approximate diameter, and its color,” added Tholen “Because 2018 VG18 is so distant, it orbits very slowly, likely taking more than 1,000 years to take one trip around the Sun.”

Astronomers are reaching farther and farther out into space in their search for objects at the limits of our Solar System. What was once considered a vast, cold emptiness is now known to be the home of several objects. And with better telescopes, computers, and research methods, astronomers may find more and more bodies in the distant reaches of our system.

“This discovery is truly an international achievement in research using telescopes located in Hawaii and Chile, operated by Japan, as well as by a consortium of research institutions and universities in the United States,” concluded Trujillo. “With new wide-field digital cameras on some of the world’s largest telescopes, we are finally exploring our Solar System’s fringes, far beyond Pluto.”

An astronomical unit is the distance from Earth to the Sun. Pluto is our Solar System’s most famous dwarf planet, and it is about 34 AU from the Sun. It took NASA’s New Horizons spacecraft nine years to get to Pluto, and Farout is about 3.5 times farther away than Pluto, so it would take about 31 years for a spacecraft to reach Farout.

Farout joins a number of other dwarf planets in the outer reaches of the Solar System. In the last few years, astronomers have discovered the Goblin, Biden, Sedna, and Eris in the region from about 80 AU to 96 AU.

The same team behind Farout’s discovery also discovered the Goblin, and 2012 VP113, also knows as Biden. Their work indicates the potential presence of an enormous planet, perhaps up to 10 times the size of Earth. In a 2016 paper, astronomers Mike Brown and Konstantin Batygin presented evidence supporting the existence of this same unseen planet with the nicknames Planet X and Planet 9. This undiscovered planet is called a super-Neptune. In their paper, the two astronomers say that the orbits of these distant dwarf planets are clustered in such a way that it can’t be an accident. There must be another large planet out there, shepherding them through space.

It’ll be a while before astronomers determine Farout’s orbit. But if it looks like it fits in with the others, that will be even more compelling evidence for the existence of the elusive Planet 9.

Sources:

• Carnegie Science Press Release: Discovered: The Most-Distant Solar System Object Ever Observed
• Carnegie Science Press Release: Solar System’s Edge Redefined
• IAU Minor Planet Center
• Research Paper: EVIDENCE FOR A DISTANT GIANT PLANET IN THE SOLAR SYSTEM
• Universe Today: New Dwarf Planet Found in the Outskirts of the Solar System, Giving Astronomers More Ammunition to Search for Evidence of Planet 9