Astronomers using the new Vera C. Rubin Observatory have found an icy object beyond Neptune that may be a new dwarf planet, CBC News, Space.com and ScienceAlert report. The find was announced on Tuesday, October 27.

The object, named 2026 ED138, is estimated to be about 600 to 1,500 kilometers across. That would make it one of the largest known dwarf planets if confirmed, CBC News reports. Only five are recognized now: Pluto, Ceres, Eris, Haumea and Makemake.

Matthew Holman of the Center for Astrophysics, Harvard and Smithsonian, spotted it on October 13 while running Rubin data through search software he built with colleague Kevin Napier. "My first reaction was one of excited disbelief," Holman said. "Objects like this are very rare."

Rubin saw the object 30 times across 20 nights between March and July. Scientists then found it in images from the Dark Energy Camera in Chile going back to 2016, Space.com and ScienceAlert report.

ScienceAlert reports the object takes about 281 years to circle the sun, citing the Minor Planet Center. It is now about 46 times as far from the sun as Earth. Its orbit is tilted about 25 degrees from the plane of the solar system, which helped it stay hidden.

To count as a dwarf planet, an object must be massive enough for its gravity to pull it into a round shape. 2026 ED138 appears big enough, but scientists must pin down its size. A small, shiny object can look as bright as a larger, darker one. Holman says observing it at longer wavelengths will help.

The Rubin Observatory sits on Cerro Pachón in Chile and has the largest digital camera ever built for astronomy.

What we know: The Rubin Observatory has found a large icy object beyond Neptune that may be a dwarf planet.
What we don't: How big the object really is, and whether it will be confirmed as a dwarf planet.