Astronomers confirm the orbit of the farthest object ever observed in our solar system

A team of astronomers, including associate professor Chad Trujillo of the Department of Astronomy and Planetary Science of northern Arizona, has confirmed a planetoid that is almost four times farther from the sun than Pluto, which is the farthest object ever in our solar system was observed. The asteroid, nicknamed ‘Farfarout’, was first detected in 2018, and the team has now collected enough observations to determine its orbit. The Minor Planet Center has now given it the official designation of AG37 2018.

Farfarout’s nickname distinguished it from the previous record holder “Farout”, which was found in 2018 by the same team of astronomers. In addition to Trujillo, the discovery team also includes Scott S. Sheppard of the Carnegie Institution for Science and David Tholen of the University of Hawaii. Institute for Astronomy, which has an ongoing survey to map the outer solar system beyond Pluto.

Farfarout will get an official name (like Sedna and other similar objects) after the track is better determined over the next few years. It was discovered at the Subaru 8-meter telescope on top of Maunakea in Hawaii, and has been recovered in recent years with the Gemini North and Magellanic telescopes to determine the orbit based on the slow motion through the air.

Farfarout’s average distance from the sun is 132 astronomical units (au); 1 au is the distance between the earth and the sun. By comparison, Pluto is only 39 au from the sun. The newly discovered object has a very elongated orbit that takes it to its furthest distance after 175 au, and within the orbit of Neptune to about 27 au, when it is close to the sun.

Farfarout’s journey around the sun lasts about a thousand years and crosses the massive planet Neptune each time. This means Farfarout probably experienced gravity interactions with Neptune during the age of the solar system, and that is why it has such a large and long orbit.

“A single orbit of Farfarout around the sun takes a millennium,” Tholen said. “Because of this long orbit, it moves very slowly through the air, requiring several years of observation to accurately determine its trajectory.”

Farfarout is very faint, and based on its brightness and distance from the sun, the team estimates its size at about 400 km, and places it at the bottom of a dwarf planet, assuming it is an icy object.

“The discovery of Farfarout shows our increasing ability to map the outer solar system and observe it further and further to the edge of our solar system,” Sheppard said. “Only with the advancement in the last few years of large digital cameras on very large telescopes has it been possible to detect objects like Farfarout efficiently. Although some of these distant objects are quite large, it is a dwarf planet in size, but it ‘is very faint because of their extreme distances from the sun. Farfarout is just the tip of the iceberg of objects in the solar system in the distant solar system.’

Since Neptune interacts strongly with Farfarout, Farfarout’s orbit and motion cannot be used to determine if there is another unknown massive planet in the very distant solar system, as these interactions dominate the orbital dynamics of Farfarout. Only objects whose orbits remain in the very distant solar system, far beyond Neptune’s gravitational influence, can be used to investigate signs of an unknown massive planet. These include Sedna and 2012 VP113, although they are currently closer to the sun than Farfarout (about 80 AU), their Neptune is never closer and will therefore rather be affected by the possible planet X.

“Farfarout’s orbital dynamics can help us understand how Neptune formed and evolved, since Farfarout was probably thrown into the outer solar system by coming too close to Neptune in the distant past,” Trujillo said. “Farfarout will probably deal strongly with Neptune again, as their orbits are still crossing.”

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