Scientists Write New Chapter for Cosmos; Discovery of Dwarf Planet, Non-Planetary Rings Challenge Theories on Solar System

Scientists Write New Chapter for Cosmos

Discovery of Dwarf Planet, Non-Planetary Rings Challenge Theories on Solar System

ROBERT LEE HOTZ

Updated March 26, 2014 6:23 p.m. ET

Scientists added two discoveries to the inventory of celestial real estate in the solar system: a dwarf planet found far beyond Pluto’s orbit, and a set of rings, like those around Saturn, that encircle a distant asteroid.

Together, the finds are spurring astronomers to rethink theories about the forces at work beyond the known planets, where millions of comets, rocks and jagged blocks of ice are suspended in vast fields of space rubble.

The findings were reported Wednesday in the journal Nature.

“There is really a lot left to explore on the outer reaches of the solar system,” said astronomer Chad Trujillo at Hawaii’s Gemini Observatory who identified the dwarf planet along with astronomer Scott Sheppard at the Carnegie Institution for Science in Washington, D.C. “This is the tip of the iceberg.”

Two new discoveries, a dwarf planet and rings around a distant asteroid, have scientists rethinking their theories about the far rim of our solar system. WSJ’s Robert Lee Hotz reports. (Photo: Scott S. Sheppard: Carnegie Institution for Science)

The pinkish miniplanet, cataloged as 2012-VP113, is about 280 miles in diameter, a little more than the distance from New York to Washington, D.C. It is located about 80 times as far from the sun as is Earth, and is most likely is made of methane and water frozen around a rocky core.

It is the second dwarf planet to turn up in a region called the inner Oort cloud, where many comets are thought to originate. The first, called Sedna, was found in 2003.

The scientists believe that these two have many neighbors yet to be identified, created from sprays of ice and gravel pulled into place by passing stars, or yanked into position by as-yet-unknown rogue planets. They may all have been planets that once circled other stars, the scientists said.

“We expect a thousand objects in this region that are bigger than a thousand kilometers in diameter,” Dr. Sheppard said. “It is possible that some are bigger than Pluto, or bigger than Mars or Earth.”

The scientists made the discovery using the Dark Energy Camera on the 4-meter telescope based at Cerro Tololo in northern Chile, which is part of the U.S. National Optical Astronomy Observatory.

Also on Wednesday, astronomers in Brazil reported the discovery of two icy rings around a distant asteroid-like object called Chariklo, which orbits the sun between Saturn and Uranus. Until now, such rings had been found only around the largest planets in the solar system.

Small by comparison, Chariklo is about 160 miles in diameter. Its outer ring appears to be about 4 miles wide and its inner ring appears to be about 2 miles wide.

“It does challenge the way we believe that planetary ring systems form,” said planetary scientist Joseph Burns at Cornell University, who wasn’t involved in the research. Until now, researchers theorized that only the largest planets had sufficient gravity to hold such rings in place.

Astronomer Felipe Braga-Ribas at Brazil’s Observatório Nacional in Rio de Janeiro organized observers at small telescopes across South America to study Chariklo as it passed in front of a star, briefly blocking its light. In his analysis, the flickering pattern of starlight revealed the presence of the rings.

“If it was a halo of dust, the signature of the light would be different,” said Dr. Braga-Ribas.

The astronomers suspect that rings around these very distant asteroids may be common. “We believe there may be many more,” he said. “The discovery opens a lot of questions.”