- Astronomers discovered a planetoid orbiting the sun further than any known object in the solar system.
- Called “Farfarout,” the object orbits the sun every 1,000 years.
- Objects like Farfarout could help astronomers figure out whether a massive planet hides in the outskirts of our solar system.
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Astronomers have discovered the most distant object ever found in our solar system.
The planetoid – the term for a small chunk of rock or dust or ice orbiting the sun – is appropriately nicknamed “Farfarout,” after the previous record-holder, “Farout,” which was discovered by the same astronomers in 2018. After years of observing the object’s trajectory across the sky, that team of researchers announced on Wednesday that they could confidently say Farfarout is, well, much farther out than any solar-system object seen before.
Farfarout is 132 astronomical units (AU) from the sun, meaning it’s 132 times farther from the sun than Earth is, and about four times as far as Pluto. It takes about 1,000 years for the planetoid to complete one orbit around the sun.
The researchers estimate that Farfarout is about 250 miles (400 kilometers) across, which would place it on the low end of being a dwarf planet like Pluto.
“The discovery of Farfarout shows our increasing ability to map the outer solar system and observe farther and farther toward the fringes of our solar system,” Scott Sheppard, one of the astronomers who discovered the object, said in a press release. Sheppard works as a researcher at the Carnegie Institution for Science.
“Only with the advancements in the last few years of large digital cameras on very large telescopes has it been possible to efficiently discover very distant objects like Farfarout,” he added. “Even though some of these distant objects are quite large – the size of dwarf planets – they are very faint because of their extreme distances from the Sun. Farfarout is just the tip of the iceberg of solar system objects in the very distant solar system.”
Finding and studying other similarly distant objects could help scientists determine whether there’s an unidentified massive planet hiding in the outskirts of our solar system. Scientists have found hints of such a planet, often referred to as Planet Nine or Planet X, in the distant dark. These clues come in the form of smaller objects whose orbital paths appear skewed.
Farfarout most likely cannot contribute to that effort, however, because Neptune appears to have significantly altered its orbit.
A snippet of a 1,000-year orbit
Farfarout crosses Neptune’s path each time it loops around the sun, and its orbit is elongated in an oval shape. At one point in the cycle, it comes as close to our star as 27 AU. But is also gets as far from the sun as 175 AU. Scientists think this strange orbit is due to Neptune’s powerful gravitational pull.
“Farfarout’s orbital dynamics can help us understand how Neptune formed and evolved, as Farfarout was likely thrown into the outer solar system by getting too close to Neptune in the distant past,” Chad Trujillo, an astronomer at Northern Arizona University who co-discovered the new object, said in the release. “Farfarout will likely interact with Neptune again in the future since their orbits still intersect.”
The Subaru Telescope, located atop Hawaii’s Maunakea, first spotted the planetoid in January 2018.
“All we knew was that the object appeared to be very distant at the time of discovery,” Sheppard said.
It took years of observation to realize just how far away it was. Because Farfarout takes so long to orbit the sun, it moves very slowly across the sky. Astronomers had to observe it for years in order to get enough data to calculate its trajectory.
The International Astronomical Union’s Minor Planet Center officially designated Farfarout as object “2018 AG37” on Wednesday. The planetoid will receive a more official name later, after further observations enable scientists to iron out its precise orbital path.
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