Welcome to Farfarout, the most distant star in the solar system and where a year lasts a thousand years

Since February 11, 2021, this star has been called 2018 AG37, as decided by the Minor Planet Center, the body responsible for naming the small bodies of the solar system (comets, asteroids, dwarf planets). But his nickname, “Farfarout” (which could be translated as “far distant”, but the pun is best enjoyed in English), should stay with him. And for good reason: it is to date the most distant body discovered in the solar system. It is located 132 astronomical units (AU) from the sun, or 132 twice the Earth-Sun distance. For the record, Pluto is “only” at 39 AU …

Discovered in 2018 but too far to “speak”

Farfarout was first spotted in January 2018 by the Subaru Telescope, located on the island of Hawaii. “At that time, we did not yet know its orbit. We only had 24 hours of observation, whereas it takes years to determine it, ”Explains co-discoverer Scott Sheppard on the National Optical-Infrared Astronomy Research Laboratory website. All they can say is that the object is obviously very far away … In November 2018, the same team discovered 2018 VG18 and they managed to estimate its distance: 124 AU. It then becomes “Farout” (distant), the most distant star, before we notice that the one discovered in January of the same year, smaller, is even further from the sun …. D ‘where this nickname, as a wink, of “Farfarout”.

On Farfarout, a year lasts 1,000 years

It therefore took the team nearly three years to determine the characteristics of the orbit of this new star at the edge of the solar system. And for good reason: it takes around 1,000 years to circle the Sun. Seen from Earth, it thus moves very slowly against the background of stars in the galaxy. Hence the three years of observations necessary to determine its orbit, with the help of two telescopes: the Gemini North telescope (Hawaii) and the Magellan telescope (Chile). This first observation campaign indicates a particular orbit, because it is very elongated. The apogee is located 175 AU from the sun, and its perigee… only 27 AU! In other words less than the orbit of Pluto, and even less than that of Neptune, which Farfarout has undoubtedly already crossed the orbit. “He was probably ejected into the Outer Solar System by getting too close to Neptune in the distant past“Says Chad Trujillo of the University of Arizona. It remains to be seen what 2018 AG37 looks like … Observations will continue to draw the portrait, and refine its orbit. But based on its low light, the team of astronomers estimated its diameter at about 400 km, six times less than Pluto, without claiming that it is indeed spherical …

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Towards “farfarfarout”?

If for the moment Farfarout holds the record of remoteness in the solar system, it will undoubtedly be temporary. “Farfarout discovery demonstrates our growing ability to map the outer solar system“says Scott Sheppard. With the progress made in recent years in digital cameras mounted on very large telescopes, it has been possible to discover very distant objects like Farfarout. But this is only the beginning…”So when will the discovery of” Farfarfarout “?

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