For a long time, Pluto was the most distant object we knew about in the solar system, but more recent observations suggest there are probably thousands of worlds lurking in the shadows on the fringes. Now astronomers are welcoming the newest and most distant member of the family – a dwarf planet orbiting more than 100 times further from the Sun than Earth. And because its discoverers apparently aren't the most creative bunch, it's been dubbed "Farout."
Officially known as 2018 VG18, the object was spotted at a distance of 120 Astronomical Units (AU) from the Sun. For reference, one AU is defined as the distance between the Earth and the Sun. As the nickname suggests, Farout is the most distant solar system object ever observed, more than three and a half times further than Pluto is right now, and comfortably beating the previous record-holder Eris, orbiting 96 AU out.
The object was first discovered in images taken on November 10, by the 8-m (26-ft) Subaru telescope in Hawaii. To map its path across the sky and take stock of its physical characteristics, follow-up observations were conducted at the Magellan telescope at Las Campanas Observatory in Chile in early December.
Due to its brightness, 2018 VG18 was estimated to be about 500 km (310 mi) wide, which is less than a quarter the size of Pluto. The color of its observed light is pinkish, suggesting it's an icy world, which makes a lot of sense given how … well, far out it is. While its orbit hasn't been pinned down completely yet, the astronomers estimate that it probably takes more than 1,000 years to complete one trip around the Sun.
Interestingly enough, while it's the most distant known solar system object right now, that might not be the case most of the time. Another dwarf planet nicknamed the "Goblin" was discovered by the same team a few months ago, and while it's currently "only" 80 AU from the Sun, its wildly eccentric, 40,000-year orbit may swing it as far away as 2,300 AU.
That extreme orbit, as well as those of other dwarf planets on the fringes of the solar system, suggest the existence of a huge planet out there somewhere. Getting a clearer idea of Farout's orbit may bring to light new clues about this enigmatic "Planet Nine."
"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," says Scott S. Sheppard, one of the discoverers of the new dwarf planet. "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."
Some scientists argue that this hypothetical Planet Nine doesn't actually exist, instead suggesting that those smaller distant objects are simply jostling each other like "gravitational bumper cars." Other teams go in the opposite direction, putting forward the idea that not only does the larger planet exist, but it's joined by a Mars-sized tenth planet.
The new object was officially announced this week by the Minor Planet Center. Along with Sheppard, astronomers David Tholen and Chad Trujillo are also credited with the discovery.
Source: Carnegie Science
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