A dwarf planet nicknamed the Goblin has been discovered well beyond Pluto, further redefining our solar system.

Key points: Frozen dwarf planet about 300km across was discovered on the outskirts of our solar system with an elongated orbit

Frozen dwarf planet about 300km across was discovered on the outskirts of our solar system with an elongated orbit Dubbed 'the Goblin', it was discovered in 2015 around Halloween, but has only now been publicly unveiled

Dubbed 'the Goblin', it was discovered in 2015 around Halloween, but has only now been publicly unveiled At its most distant, the Goblin is 2,300 times further from the sun than Earth is

A round frozen world just 300 kilometres across, the Goblin was spotted by astronomers in 2015 around Halloween, thus its spooky name. But it wasn't publicly unveiled until now following further observations with ground telescopes.

One of the astronomers who made the discovery, Scott Sheppard of the Carnegie Institution for Science, said the Goblin was on the small end for a dwarf planet. It is officially known as 2015 TG387 by the International Astronomical Union's Minor Planet Centre.

This is the third dwarf planet recently found to be orbiting on the frigid fringes of our solar system.

Goblin's orbit is extremely elongated — so stretched out, in fact, that it takes 40,000 years for it to circle the sun.

At its most distant, the Goblin is 2,300 times further from the sun than Earth. That's 2,300 astronomical units (AU). One AU is the distance from Earth to the sun, or roughly 150 million kilometres.

At its closest, the Goblin is 65 times farther from the sun than Earth, or 65 AU. Pluto, by comparison, is approximately between 30 and 50 AU.

The Goblin has an extremely elongated orbit that takes it up to 2,300 times further from the sun than Earth is. ( Carnegie Institution for Science )

Dr Sheppard, along with Northern Arizona University's Chad Trujillo and the University of Hawaii's David Tholen, spotted the Goblin in October 2015 when it was relatively nearby — around 80 AU.

Scientists still pursuing elusive 'Planet X'

The two other dwarf planets are Sedna, discovered in 2003, which is about 1,000km across, and 2012 VP113, about 500km across. They were found by some of the same astronomers.

Thousands — even a million — more such objects could be way out there orbiting in the so-called Inner Oort Cloud, according to the researchers. They're in hot pursuit of them, as well as a potentially bigger-than-Earth planet known as Planet 9, or Planet X, believed by some scientists to be orbiting at a distance of hundreds of AU.

"These objects are on elongated orbits, and we can only detect them when they are closest to the Sun. For some 99 per cent of their orbits, they are too distant and thus too faint for us to observe them. We are only seeing the tip of the iceberg," Dr Sheppard said.

Dr Sheppard said the faraway objects were "like breadcrumbs leading us to Planet X."

"The more of them we can find, the better we can understand the outer solar system and the possible planet that we think is shaping their orbits — a discovery that would redefine our knowledge of the solar system's evolution," he said in a statement.

AP