Extremely distant solar system object discovered

Scientists have discovered a distant object at the edge of the solar system, which completes one orbit around the Sun every 40,000 years, a finding that supports the presence of Planet X.

The newly found object, called 2015 TG387, was discovered about 80 astronomical units (AU) from the Sun.

AU is a measurement defined as the distance between Earth and the Sun. For context, Pluto is around 34 AU, so 2015 TG387 is about two and a half times further away from the Sun than Pluto is right now.

The object is on a very elongated orbit and never comes closer to the Sun, a point called perihelion, than about 65 AU, according to researchers from the Carnegie Institution for Science in the US.

Only 2012 VP113 and Sedna at 80 and 76 AU respectively have more-distant perihelia than 2015 TG387.

Though 2015 TG387 has the third-most-distant perihelion, its orbital semi-major axis is larger than 2012 VP113 and Sedna's, meaning it travels much farther from the Sun than they do.

At its furthest point, it reaches all the way out to about 2,300 AU. 2015 TG387 is one of the few known objects that never comes close enough to the solar system's giant planets, like Neptune and Jupiter, to have significant gravitational interactions with them.

"These so-called Inner Oort Cloud objects like 2015 TG387, 2012 VP113, and Sedna are isolated from most of the Solar System's known mass, which makes them immensely interesting," said Scott Sheppard, from Carnegie.

"They can be used as probes to understand what is happening at the edge of our Solar System," said Sheppard.

The object with the most-distant orbit at perihelion, 2012 VP113, was also discovered by Sheppard and Trujillo, who announced that find in 2014.

The discovery of 2012 VP113 led Sheppard and Trujillo to notice similarities of the orbits of several extremely distant solar system objects, and they proposed the presence of an unknown planet several times larger than Earth -- sometimes called Planet X or Planet 9 -- orbiting the Sun well beyond Pluto at hundreds of AUs.

"We think there could be thousands of small bodies like 2015 TG387 out on the Solar System's fringes, but their distance makes finding them very difficult," said David Tholen from University of Hawaii.

"Currently we would only detect 2015 TG387 when it is near its closest approach to the Sun. For some 99 per cent of its 40,000-year orbit, it would be too faint to see," he said.

The object was discovered as part of the team's ongoing hunt for unknown dwarf planets and Planet X. It is the largest and deepest survey ever conducted for distant Solar System objects.