Astronomers have found a dwarf planet three times farther away from the Sun than Pluto, making it the most distant known object in the solar system. Designated V774104, the trans-Neptunian object is 500 to 1000 kilometres in diameter — half the size of Pluto — and currently lies 15.4 billion kilometres (9.6 billion miles) or 103 astronomical units (AU) from the Sun, but its exact orbit is yet to be determined.
The discovery was announced by Scott Sheppard, an astronomer at the Carnegie Institution for Science in Washington, D.C. at the 47th Annual Meeting of the Division for Planetary Sciences of the American Astronomical Society this week. The team behind the find is led by Sheppard and Chad Trujillo, from the Gemini Observatory in Hawaii.
Sheppard made his discovery with colleagues last month using Japan’s 8-metre Subaru Telescope in Hawaii. Unlike many searches for distant objects, which peer into the ecliptic, Sheppard is training Subaru on swaths of the sky an average of 15 degrees away from the solar system’s plane.“It could end up joining an emerging class of extreme solar system objects whose strange orbits point to the hypothetical influence of rogue planets or nearby stars,” said a report in the journal Science. The discovery of V774104 is fuelling speculation that an as-yet-undiscovered large planet is hiding in the furthest reaches of the solar system.
“The discovery of V774104 is more proof that the solar system is bigger than we thought,” said Joseph Burns, professor of engineering and astronomy at Cornell University. “We need a little more time to pin down the orbit and determine the object’s exact size, but it must be big to see it at this distance.”
Previously, the most distant solar system object was announced in 2005 — a dwarf planet named Eris that was 97 AU from the Sun. (One astronomical unit is the distance between Earth and the Sun.) Mike Brown, a planetary astronomer at the California Institute of Technology in Pasadena and discoverer of Eris, acknowledges that he will have to give up the claim to having discovered the most distant solar system object. “I have held the record for 10 years,” he says, jokingly. “I have to relinquish it. So I’m sad.”
At the time of V774104’s discovery, only the Voyager probes, Pioneer 10 and some long-period comets are known to be farther from the Sun.