Beyond Pluto: Observatory reveals new dwarf planet candidate

Astronomers have just spotted a small, bright world in the outer reaches of the solar system they think could be a dwarf planet like Pluto. 

The mysterious space object, for now known as 2026 ED138, lies about 46 times farther from the sun than Earth, and may measure between 370 to 930 miles wide. Scientists estimate it’s about 1.1 billion miles farther than Pluto in the Kuiper Belt, a zone of icy debris past Neptune.

Matthew Holman, a researcher at the Harvard & Smithsonian Center for Astrophysics, made the discovery two weeks ago by running data from the new Vera C. Rubin Observatory through a program he built with fellow astronomer Kevin Napier. 

“My first reaction was one of excited disbelief,” Holman said in a statement. “Objects like this are very rare, so I immediately started checking whether I or the code had done something wrong.”

The International Astronomical Union’s Minor Planet Center, the official recordkeeper for new objects in our solar system, announced it as a candidate on Wednesday. If confirmed, ED138 could become the sixth officially recognized dwarf planet in the solar system, following Ceres, Pluto, Haumea, Makemake, and Eris. 

Rubin’s detection of a previously unknown world in our own cosmic backyard highlights a new accelerated way of doing astronomy. After the initial find, the team was able to piece together a detailed “picture” of the object in three days. By pairing the observatory’s repeated sky scans with archival data and pictures from other telescopes, the researchers learned quite a bit about ED138 and its stretched orbit around the sun. 

You can think of a dwarf planet as a scaled-down planet. It gets pulled around the sun by its own gravity, but it’s not quite massive enough to clear other space rocks out of its way like a regular planet does. Pluto’s 2006 demotion from planet status occurred because other icy bodies cross its orbit. 

“Once we identify a new object, we can search back months, and sometimes even decades, finding it in images where nobody knew to look,” said Mario Jurić, Rubin’s lead solar system scientist at the University of Washington, in a statement. “This ability to both discover and ‘precover’ objects is transforming how quickly and accurately we can determine their orbits and understand the distant solar system.”

Astronomers say ED138 shines so brightly that folks with fairly small telescopes could probably see it. The reason no one has noticed it until now may be that it hides in plain sight among the Milky Way‘s crowded band of stars in the sky. 

Want more science and tech news delivered straight to your inbox? Sign up for Mashable’s Light Speed newsletter or get Mashable push alerts today.

Looking back in the vault, Rubin’s Simonyi Survey Telescope had observed ED138 some 30 times between March 4 and July 11. Then, using the Asteroid Institute’s ADAM Precovery tool, which combs archives for old matches to newly found objects, the team saw it again in 2016 images taken with the Dark Energy Camera at another observatory in Chile. Combined, the data allowed astronomers to trace the object’s path over a decade. 

For now, scientists call ED138 a dwarf planet candidate because they still need to prove it’s round. Icy objects of this size usually get pulled into a round shape by their own gravity. To be sure, though, scientists need to observe it with other telescopes in infrared light — a kind of light our eyes can’t see — to pin down its exact size and other details.

Distant objects like ED138 are artifacts from the era when the planets, including Earth, formed, and they could help explain how the solar system and its giant planets came together.

Over the next 10 years, Rubin will photograph the whole southern sky repeatedly. Scientists believe this new detection is just the beginning of many discoveries to come. 

“Any others hiding in the places earlier surveys skipped are now within reach,” Holman said.