Astronomers have discovered a widespread world that circles the sun.
How far out? It’s as far out as the detectives nicknamed the “Farout”. All they can see is a pink dot of light in the night sky, but it is enough to conclude that they are looking at a 300-mile iceball that revolves over 11 billion miles from the sun – more than three times as far as Pluto, and the longest the object ever observed in the solar system.
is the latest revelation in a distant region that was once expected to be empty, and studying its path can help point to an even invisible ninth planet that circles the sun far beyond Neptune.
“Last month we came across it very, very slowly,” said Scott S. Sheppard of Carnegie Institution for Science, one of the discoverers of VG18. “Immediately we knew it was an interesting item.”
The sun’s gravity decreases with distance. Far more distant worlds move slowly and take longer to complete an orbit than closer. A languid dim light spot appeared in pictures taken November 10th by the Japanese Subaru 8 meter telescope located on top of Mauna Kea in Hawaii. Follow-up observations at Las Campana’s observatory in Chile this month confirmed the discovery.
Planetary researchers often use the distance from the sun to the ground – defined as an astronomical unit, or 93 million miles – as a meter for measuring the solar system. The neptune is 30 astronomical units gone, or 2.8 billion miles, and Pluto, currently on the outer leg in its orbit, is 34.5 astronomical units, or 3.2 billion miles from the sun.
Farout was observed by Subaru Telescope at the Mauna Kea Observatory in Hawaii, November 10th. In the hour between exposures, the object moved relative to the background stars and galaxies. Credit Scott S. Sheppard and David Tholen / Carnegie Department of Science
Pluto was once considered as the outer edge of the solar system. But from 1992, astronomers discovered a variety of other hollow worlds beyond Neptune, a region now called the Kuiperbelt. The coop belt ends at a distance of about 50 astronomical units, and the space outside it believed to be largely empty.
However, astronomers now discover objects like VG18 in this region and are still sure how to explain how all of them got there.
VG18 is 120 to 130 astronomical units from the sun. It is the first solar system object ever discovered at a distance of more than 100 astronomical units. (Other objects are known to have paths that turn far beyond 100 astronomical units, but are currently closer.)
Astronomers still do not have a good sense of VG18’s path – whether it is elliptical and zooming in near Neptune or if it’s more circular and always stays far away. This information, which may require a few years of further observations, will tell if it fits a prediction of a distant planet larger than the Earth, but less than Neptune.
So far, they can report that VG18 has a pink shade and, provided it is moderately dark, guess it’s about 300 miles wide. A trip around the sun probably takes at least 1000 years. If VG18 really is so large, it would probably be massive enough for gravity to drag it in a round shape and fulfill the definition of a “dwarf plan”, the same category that includes the asteroid Ceres and the former planet Pluto.
Dr. Sheppard and his colleagues, like other astronomers, chart the sky for the hypothetical giant planet, often called Planet Nine. So far, their searches have proved to be just exciting clues. In October, Dr Sheppard and his colleagues reported the discovery of a remote world, albeit not as distant as VG18. They nicknamed Goblin, as Halloween approaches, and its circulation provided additional evidence that Planet Nine could really exist.
VG18 is close to what the current telescope can detect. But it is probably not the latest discovery that will be made in the latter regions. Dr Sheppard said, “If it’s longer, then we’ll call it Way, Way Out or something.”