the most distant known object in the Solar System

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A team of astronomers has just confirmed the existence of the most distant known object in the Solar System. It is about 400 kilometers in diameter and could complete one revolution of the Sun in more than 800 years.

In February 2019, a team of astronomers led by Scott Sheppard, from the Carnegie Institution for Science (United States), announced that they had identified an object about 132 astronomical units (AU) from the Sun (one AU is equivalent to the Earth – Sun distance , or about 150 million km). If the discovery were to be confirmed, it could therefore be the most distant body ever spotted in the Solar System.

Presence confirmed!

However, it is now done. Originally named “FarFarOut” (very, very far), it is provisionally baptized 2018 GA 37, while waiting for the real baptism by the International Astronomical Union. These new observations also allowed researchers to characterize the object a little. We now know that it measures approximately four hundred kilometers in diameter.

The object is finally positioned at 101 astronomical units the Sun, 101 times the distance between the Earth and the Sun. It’s a little closer than initially assumed. It remains, however, the most distant known object in the Solar System. For comparison, Pluto is at an average orbital distance of about 39 astronomical units.

Note that this is an average distance. On its orbit around the Sun, very “oval”, the object can move away up to 175 astronomical units of our star and approach it to 27 astronomical units, which brings him back inside the orbit of Neptune. Moreover, the latter could have been involved in the “return” of the object.

FarFarOut was likely thrown back to the Outer Solar System by getting too close to Neptune in the distant past“, to propose astronomer Chad Trujillo of Northern Arizona University. “It will likely interact with Neptune again in the future since their orbits still intersect.“.

Artist’s impression of FarFarOut. Credits: NOIRLab / NSF / AURA / J. Da Silva

Further observations to come

The object remains however still very mysterious. And for good reason: it is extremely weak and has only been observed nine times in two years. We do not yet know, for example, if it is a “simple” very large irregular object of the kuiper belt or if it could meet the criteria to be classified as a dwarf planet.

Astronomers are also not entirely sure of its orbit. They nevertheless suggest that the object could complete a revolution of the Sun in a little less than eight hundred years. Additional observations will obviously be necessary in order to attempt to answer these questions.

FarFarOut really takes its time to go around the Sun“, Continues David Tholen of the University of Hawaii at Mānoa. “It therefore moves very slowly in the sky, which requires several years of observations to precisely determine its trajectory.“.

At the base, Sheppard, Tholen and Trujillo work together on the study of the Outer Solar System in the hopes of one day being able to stumble upon the mysterious “new planet”, a gigantic, but still hypothetical object, supposed to evolve in the far reaches of our System. More recently, these same researchers have also discovered twelve additional moons orbiting Jupiter, but also twenty other moons orbiting Saturn.

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