A new dwarf planet, called 2012 VP113, has been found beyond the known edge of the Solar System in an area called the inner Oort cloud.
The Carnegie Institution for Science’s Scott Sheppard and Chadwick Trujillo of the Gemini Observatory say discovery is likely to be one of thousands of distant objects thought to form the Oort cloud.
Their work also indicates the potential presence of an enormous planet, perhaps up to 10 times the size of Earth, not yet seen but possibly influencing the orbit of 2012 VP113 as well as other inner Oort cloud objects.
Their findings are published today in the journal in Nature.
The known Solar System can be divided into three parts: the rocky planets such Earth, which are close to the Sun; the gas giant planets, which are further out; and the frozen objects of the Kuiper belt, which lie just beyond Neptune’s orbit.
Beyond this there appears to be an edge to the Solar System where only one object, Sedna, was previously known to exist for its entire orbit. But the newly found 2012 VP113 has an orbit which stays even beyond Sedna, making it the furthest known in the Solar System.
“This is an extraordinary result that redefines our understanding of our Solar System,” says Linda Elkins-Tanton, director of Carnegie’s Department of Terrestrial Magnetism.
Sedna was discovered beyond the Kuiper Belt edge in 2003 and it was not known if it was unique as Pluto once was thought to be before the Kuiper Belt was discovered.
With the discovery of 2012 VP113 it is now clear Sedna is not unique and is likely the second known member of the hypothesised inner Oort cloud, the likely origin of some comets.
2012 VP113’s closest orbit point to the Sun brings it to about 80 times the distance of the Earth from the Sun, a measurement referred to as an astronomical unit or AU.
The rocky planets and asteroids exist at distances ranging between .39 and 4.2 AU. Gas giants are found between 5 and 30 AU, and the Kuiper belt (composed of thousands of icy objects, including Pluto) ranges from 30 to 50 AU. In our solar system there is a distinct edge at 50 AU. Only Sedna was known to stay significantly beyond this outer boundary at 76 AU for its entire orbit.
“The search for these distant inner Oort cloud objects beyond Sedna and 2012 VP113 should continue, as they could tell us a lot about how our Solar System formed and evolved,” says Sheppard.
Sheppard and Trujillo used the new Dark Energy Camera on the NOAO 4 meter telescope in Chile for discovery. It has the largest field-of-view of any 4-metre or larger telescope, giving it unprecedented ability to search large areas of sky for faint objects.
From the amount of sky searched, Sheppard and Trujillo determine that about 900 objects with orbits like Sedna and 2012 VP113 with sizes larger than 1,000 kilometres may exist and that the total population of the inner Oort cloud is likely bigger than that of the Kuiper Belt and main asteroid belt.
“Some of these inner Oort cloud objects could rival the size of Mars or even Earth. This is because many of the inner Oort cloud objects are so distant that even very large ones would be too faint to detect with current technology”, says Sheppard.
There are three competing theories for how the inner Oort cloud might have formed. As more objects are found, it will be easier to narrow down which of these theories is most likely accurate.
One theory is that a rogue planet could have been tossed out of the giant planet region and could have perturbed objects out of the Kuiper Belt to the inner Oort cloud on its way out.
This planet could have been ejected or still be in the distant solar system today. The second theory is that a close stellar encounter could put objects into the inner Oort cloud region. A third theory suggests inner Oort cloud objects are captured extra-solar planets from other stars that were near our Sun in its birth cluster.
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