Asteroid discovered in the "backyard" of the Solar System

After a decade of searching, astronomers have discovered a second dwarf planet with an orbit far beyond Pluto, but still can't explain how it got there.

Simulated image of asteroid Sedna. (Source: Reuters)

This tiny planet, now tentatively named "2012 VP 113" by the International Minor Planet Center, has an estimated diameter of just over 450km, less than half the size of its "neighboring" dwarf planet Sedna, discovered in 2003.

Sedna and VP 113 are the first objects found in a region of the Solar System previously thought to be devoid of any planets.

This supposedly desolate region stretches from the outer edge of the Kuiper belt, home to Pluto and more than 1,000 other small icy bodies, to the Oort cloud, which orbits the Sun about 10,000 times farther than Earth does.

“When Sedna was discovered 10 years ago, it almost redefined what we thought about the solar system,” astronomer Scott Sheppard of the Carnegie Institution in Washington DC said in an interview.

No event in the modern solar system could explain the existence of Sedna and VP 113, astronomers say in a study published Wednesday in the journal Nature.

Sedna's 11,400-year orbit around the Sun is about 76 times the distance that Earth orbits the Sun. VP 113's closest approach to the Sun is 80 times farther than Earth's orbit - nearly twice as far as the Kuiper Belt.

“Given the current architecture of the solar system, Sedna and 2012 VP 113 should not be there,” Megan Schwamb, an astronomer at the Academia Sinica in Taipei, Taiwan, wrote in a paper published in Nature.

Computer simulations suggest several possible scenarios. Lead researcher Chad Trujillo favors the idea that a star formed in the same stellar nursery as the Sun, and due to the influence of gravity, collided and ejected some of the Oort cloud entities into the interior.

Sheppard, however, thinks that another planet at least as large as Earth may have been ejected from the solar system and taken with it a number of Kuiper Belt objects. These planets may still be in the far reaches of the solar system, too dim and isolated to be detected by telescopes or cameras, Sheppard said.

The third option is that the Sun has a companion, an entity five to 10 times the mass of Earth, with enough gravity to drag Sedna, VP 113, and possibly 10 million other dwarf planets into strange and distant orbits.

“With the discovery of a second dwarf planet, we cannot rule out any hypothesis,” Trujillo said.

It is possible that more objects in the inner region of the Oort cloud will be discovered in the future.

Astronomers are trying to confirm the existence of six planets like Sedna, which was discovered last year. This means imaging the asteroids several times a year, or even more, to measure how they move relative to their stars.

“They are really hard to find,” Trujillo shares.

Astronomers believe there could be as many as 150 million dwarf planets like Sedna, with diameters ranging from about 50 to more than 8,000km, larger in both number and size than the Kuiper belt objects.

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