A team of astronomers has just confirmed the existence of the most distant known object in the Solar System. It measures 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 at about 132 astronomical units (AU ) of the Sun (one AU is equivalent to the Earth-Sun distance, i.e. 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.
It is now done. Initially named "FarFarOut" (very, very far), it is provisionally named 2018 AG 37 , pending actual baptism by the International Astronomical Union. These new observations also allowed the researchers to characterize the object a little. We now know that it is about four hundred kilometers in diameter .
The object finally positions itself at 101 astronomical units of the Sun, or 101 times the distance between the Earth and the Sun. It's a bit closer than originally assumed. However, it remains the farthest 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. In its orbit around the Sun, very "oval", the object can move away up to 175 astronomical units our star and approach it within 27 astronomical units , bringing it back inside Neptune's orbit. In fact, she may have been involved in "returning" the object.
"FarFarOut was likely thrown back to the outer Solar System by getting too close to Neptune in the distant past “, suggests astronomer Chad Trujillo, of Northern Arizona University. "It will probably interact with Neptune again in the future since their orbits always cross “.
The object is still very mysterious, however. 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 aren't entirely sure of its orbit either. 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 to try to answer these questions.
"FarFarOut really takes its time going 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 “.
Basically, Sheppard, Tholen, and Trujillo work together on the study of the outer Solar System in hopes of one day being able to stumble upon the mysterious "Planet Nine", a gigantic, but still hypothetical object, supposed to evolve in the confines of our System. More recently, these same researchers also discovered twelve additional moons orbiting Jupiter, as well as twenty other moons orbiting Saturn.
