Small World Discovered Far Beyond Pluto
NY Times: http://www.nytimes.com/2014/03...
Discovery of Planetoid Hints at Bigger Cousin in Shadows
By KENNETH CHANGMARCH 26, 2014
Astronomers have discovered a second icy world orbiting in a slice of the solar system where, according to their best understanding, there should have been none.
“They’re in no man’s land,” Scott S. Sheppard, of the Carnegie Institution for Science in Washington, said of the objects, which orbit far beyond the planets and even the ring of icy debris beyond Neptune known as the Kuiper belt.
Intriguingly, the astronomers said that details of the orbits hint at perhaps an unseen planet several times the size of Earth at the solar system’s distant outskirts.
The new planetoid, an estimated 250 miles wide, is now 7.7 billion miles from the sun, about as close as it gets. At the other end of its orbit, the planetoid, which for now carries the unwieldy designation of 2012 VP113, loops out to a distance of 42 billion miles. Neptune, by contrast, is a mere 2.8 billion miles from the sun.
Much farther out, a trillion miles, the solar system is believed to be surrounded by a sphere of icy bodies known as the Oort cloud, where many comets are thought to originate. But between the Kuiper belt and the Oort cloud, astronomers had expected empty space.
In 2003, astronomers unexpectedly discovered the planetoid Sedna, orbiting the sun beyond the Kuiper Belt, an area of frozen objects just outside Neptune’s orbit. Astronomers have now discovered a second object in this region, which has the current designation 2012 VP113.
Source: Scott S. Sheppard/ Carnegie Institution for Science
The discovery, by Dr. Sheppard and Chadwick A. Trujillo of the Gemini Observatory in Hawaii, is reported in the journal Nature.
For convenience, the scientists shortened the 2012 VP113 designation to VP, which in turn inspired their nickname for the planetoid: Biden, after Vice President Joseph R. Biden. Dr. Trujillo said they had not decided what to propose for the official name.
The existence of 2012 VP113 could help explain why there is anything out there at all.
In the 2000s, when Michael E. Brown, an astronomer at the California Institute of Technology, scanned the outer solar system, his biggest discovery was Eris, a ball of ice in the Kuiper belt that was Pluto-size or slightly bigger, the impetus for the demotion of Pluto to dwarf planet.
Dr. Brown’s oddest discovery, however, came a couple of years earlier: Sedna, a 600-mile-wide planetoid also beyond the Kuiper belt, three times as far from the sun as Neptune. Its 11,400-year orbit stretches farther than that of 2012 VP113.
In the youth of the solar system, there would not have been enough matter out there to coalesce into something as large as Sedna. It was too far out to have been flung by the gravitational slings of big planets, but too close to have been nudged by the gravitational tides of the Milky Way.
Having found one such body, astronomers expected to quickly find more, and they came up with a name for them: Sednoids. But for years, no one found any.
For the latest search, Dr. Trujillo and Dr. Sheppard used a 13-foot telescope at the Cerro Tololo Inter-American Observatory in Chile. In November 2012, they spotted a moving point of light beyond the Kuiper belt — 2012 VP113. Follow-up observations last year confirmed it was a Sednoid. Scientists have come up with various ideas to explain such bodies. Dr. Brown, for one, thinks the Sednoids were pushed there when the sun was part of a dense cluster of stars — “a fossil record of the birth of the solar system,” he said.
Others suggest that a rogue planet, ejected from the inner solar system, dragged the Sednoids along as it flew through the Kuiper belt. Dr. Trujillo and Dr. Sheppard point out that the orbits of Sedna and 2012 VP113 have similarities to those of several other Kuiper belt bodies, which could be a sign of an unseen planet’s gravitational influence.
Computer simulations showed that the similarities could be explained by a planet with a mass five times that of Earth about 23 billion miles from the sun, too dim to be seen.
Harold F. Levison of the Southwest Research Institute in Boulder, Colo., who models the beginning of the solar system, agreed that this was a possibility. “I think they’ve convinced me there’s something going on,” he said of Dr. Trujillo and Dr. Sheppard. “But I think it’s too early to say that it’s a planet.”
The astronomers expect to find more Sednoids in the next few years, which could solve the mystery of their origin. “When we find 10 of them, I’ll tell you what the answer is,” Dr. Brown said.
Los Angeles Times: http://www.latimes.com/science...
By Amina Khan
March 26, 2014, 12:53 p.m.
Astronomers searching for the faintest glimmers of light beyond distant Pluto say they’ve discovered a new dwarf planet – and that this planetoid’s movements hint that an invisible giant planet perhaps 10 times the size of Earth could be lurking around the dark fringes of our solar system.
The new dwarf planet 2012 VP-113, described Wednesday in the journal Nature, helps confirm the existence of an “inner Oort cloud” in an interplanetary no man’s land that was once thought to be empty but could potentially be teeming with rocky denizens.
“We had high hopes, and our hopes were confirmed,” said Scott Sheppard, an astronomer at the Carnegie Institution for Science who co-wrote the paper with Chadwick Trujillo of the Gemini Observatory in Hawaii.
2012 VP-113 measures about 280 miles across and comes to within about 80 astronomical units of the sun, or about 7.4 billion miles. (One astronomical unit is the distance between the Earth and the sun.) That’s far beyond the Kuiper belt, an icy field of debris that sits beyond Neptune’s orbit between 30 and 55 astronomical units.
While the dwarf planet is incredibly far out, it’s still not far enough to be part of the Oort cloud, a hypothesized cloud of icy debris that surrounds the solar system’s disc in a spherical shell that stretches a mind-blowing 5,000 to 100,000 astronomical units from the sun. 2012 VP-113’s orbit stretches for a few hundred astronomical units, in what scientists thought was an empty doughnut ring of space between the Oort cloud and the Kuiper belt.
That assumption began to change in 2003 with the discovery of Sedna sitting near the inner edge of this no man’s land. Roughly 600 miles wide, Sedna is big enough to qualify as a dwarf planet. So scientists were puzzled: Was Sedna a freakish one-off, or was it part of a population of rocky bodies in that supposedly empty area – an inner Oort cloud?
An inner Oort cloud would be valuable to study, scientists said, because these objects are so far away from the gravitational pull of either the planets or the distant stars that they’re like a dynamic “fossil” of interplanetary movement in the early solar system.
Sheppard and Trujillo wanted to look for more Sedna-like objects in this area; if they could find more, they’d show that it wasn’t an anomaly.
Looking for such distant, dim objects is not easy. Unlike the distant stars in the night sky, rocks don’t make their own light. So the astronomers have to look for faint, moving glints of reflected sunlight off these distant bodies. That means the sun’s rays have to travel all the way out to this dark, cold interplanetary fringe and then come all the way back to us.
The researchers used the Dark Energy Camera (DECam) on the NOAO 4-meter telescope in Chile and scanned the sky looking for such dim, slow-moving objects. After months of analysis, the scientists picked up on an intriguing signal in the sky.
“It was the slowest moving thing I’d seen in the discovery process, so immediately I knew it was interesting,” Sheppard said of finding 2012 VP-113. “It was very exciting to know that you’ve discovered this object that’s way out there.”
The scientists estimated that there could be about 1,000 objects in the inner Oort cloud with diameters of 1,000 kilometers or greater – and some of them could be as large as Mars.
What’s more, Sedna and 2012 VP-113 seem to be making their closest approach to the sun at similar angles – which could mean that there’s a giant planet out there, tugging at both of their orbits in the same way. This ghost planet could be from 1 to 20 Earth masses, Sheppard said, though it’s still also possible that the dwarf planets were pulled there by the tug from a passing star in the sun’s early history.
“It’s not a complete explanation, but it’s a possible explanation,” said UCLA astronomer David Jewitt, who first discovered Kuiper belt objects and was not involved in the new discovery.
Astronomers will have to find far more of these distant objects and catch enough of them traveling in the same direction before they can say whether a giant planet is lurking in the inner Oort cloud, Jewitt said.
“It isn’t watertight,” he added, “but it’s very, very interesting.”