NASA Supported Research Helps Redefine Solar System's Edge

The solar system has a new most-distant family member.

Scientists using ground based observatories have discovered an object that is believed to have the most distant orbit found beyond the known edge of our solar system. Named 2012 VP113, the observations of the object -- possibly a dwarf planet -- were obtained and analyzed with a grant from NASA. A dwarf planet is an object in orbit around the sun that is large enough to have its own gravity pull itself into a spherical, or nearly round, shape.

The detailed findings are published in the March 27 edition of Nature.

“This discovery adds the most distant address thus far to our solar system’s dynamic neighborhood map,” said Kelly Fast, discipline scientist for NASA's Planetary Astronomy Program, Science Mission Directorate (SMD) at NASA Headquarters, Washington. “While the very existence of the inner Oort Cloud is only a working hypothesis, this finding could help answer how it may have formed.”

The observations and analysis were led and coordinated by Chadwick Trujillo of the Gemini Observatory in Hawaii and Scott Sheppard of the Carnegie Institution in Washington. They used the National Optical Astronomy Observatory’s 13-foot (4-meter) telescope in Chile to discover 2012 VP113. The telescope is operated by the Foundation of Universities for Research in Astronomy, under contract with the National Science Foundation. The Magellan 21-foot (6.5-meter) telescope at Carnegie’s Las Campanas Observatory in Chile was used to determine the orbit of 2012 VP113 and obtain detailed information about its surface properties.

“The discovery of 2012 VP113 shows us that the outer reaches of our solar system are not an empty wasteland as once was thought,” said Trujillo, lead author and astronomer. “Instead, this is just the tip of the iceberg telling us that there are many inner Oort Cloud bodies awaiting discovery. It also illustrates how little we know about the most distant parts of our solar system and how much there is left to explore.”

Our known solar system consists of the rocky planets like 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 somewhat smaller than Pluto, Sedna, was previously known to inhabit for its entire orbit. But the newly found 2012 VP113 has an orbit that stays even beyond Sedna, making it the furthest known in the solar system.

Sedna was discovered beyond the Kuiper Belt edge in 2003, and it was not known if Sedna was unique, as Pluto once was thought to be before the Kuiper Belt was discovered in 1992. With the discovery of 2012 VP113, Sedna is not unique, and 2012 VP113 is likely the second known member of the hypothesized inner Oort cloud. The outer Oort cloud is the likely origin of some comets.

“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 determine that about 900 objects with orbits like Sedna and 2012 VP113 with sizes larger than 621 miles (1000 km) may exist. 2012 VP113 is likely one of hundreds of thousands of distant objects that inhabit the region in our solar system scientists refer to as the inner Oort cloud. 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,” said Sheppard. 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.”

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 hundreds 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. Until 2012 VP113 was discovered, only Sedna, with a closest approach to the Sun of 76 AU, was known to stay significantly beyond this outer boundary for its entire orbit.

Both Sedna and 2012 VP113 were found near their closest approach to the sun, but they both have orbits that go out to hundreds of AU, at which point they would be too faint to discover. The similarity in the orbits found for Sedna, 2012 VP113 and a few other objects near the edge of the Kuiper Belt suggests the new object’s orbit might be influenced by the potential presence of a yet unseen planet perhaps up to 10 times the size of Earth. Further studies of this deep space arena will continue.