How Far Away Is Farfarout?

What object in our solar system is farthest away from the sun? At one time, this honor went to a trans-Neptunian object officially designated 2018 VG18 (but nicknamed Farout) that was estimated to be 124 AU from the sun. To explain, a trans-Neptunian object is any minor or dwarf planet that orbits the sun at a greater average distance than the planet Neptune. And AU stands for astronomical unit, another way to measure long distances in space: one AU is the average distance from the center of the earth to the center of the sun, about 93 million miles (150 million km).

But science marches on, and now we have a new record-holder. An object was discovered in January 2018 that, after a couple of more years of observations, has now been declared the farthest object in the solar system yet discovered. It’s been given an official designation 2018 AG37, but originally it was referred to as (wait for it) Farfarout.

This illustration imagines what the distant object nicknamed “Farfarout” might look like in the outer reaches of our solar system. Estimated to be about 250 miles (400 km) across, Farfarout is shown in the lower right, while the sun appears in the upper left. The Milky Way stretches diagonally across the background. Image via NOIRLab/ NSF/ AURA/ J. da Silva.

This discovery took years to verify because Farfarout is so ‘far out’ that extra time was needed to learn its characteristics. It’s estimated to be about 250 miles across, barely a dwarf planet. And not surprisingly, it has a huge orbit that takes more than a thousand years to complete. But this orbit is highly elliptical, ranging from 27 AU to 175 AU from the sun. At times, it’s actually inside Neptune’s orbit, which gives a clue as to what probably happened — a close encounter with Neptune could’ve stretched its path to such extreme dimensions.

By the way, there are thought to be objects in our solar system that are even farther out, like the comets in the Oort Cloud, which could dwell between 2,000 and 50,000 AU from the sun. Or maybe more dwarf planets; right now we just don’t know.

One thing is for sure — our solar system, cosmically small as it is, is still very, very big.

Taken from the EarthSky website: “Farthest Know Object in the Solar System Identified” (https://earthsky.org/space/farthest-known-object-solar-system-farfarout?).

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