Space is vast, with trillions of objects in it, so it’s not necessarily a surprise when scientists find new objects there, even if it’s sometimes entirely by accident. Some objects are scarcer than others, and dwarf planets in our solar system are among the rarest, with only five recognized examples. A group of researchers from the Vera C. Rubin Observatory may have just found a sixth. 

Meet ED138, a dwarf planet candidate. It was found earlier in October when Rubin Operations team member Matthew Holman noted an unusually large object uncovered by a program he’d written with colleague Kevin Napier to scan Rubin Observatory data for moving objects. 

“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.”

Holman ran the search a second time through archived data and found the same object 20 more times dating back to March 2026. He checked even more data from the Dark Energy Camera at the US National Optical-Infrared Astronomy Research Laboratory and the Asteroid Institute’s Asteroid Discovery Analysis and Mapping Precovery service, and found the object in observations going all the way back to 2016.  

What makes a dwarf planet?

Researchers at the Rubin Observatory are hopeful, since ED138 seems to have all the properties of a dwarf planet. It’s further away from the sun than Neptune, which classifies it as a trans-Neptunian object. Not all TNOs are dwarf planet candidates, but ED138 is also the right size and shape. Based on preliminary estimates, the icy body is between 600 and 1,500 kilometers wide, which should be large enough for its shape to be round due to the pull of its own gravity. 

The discovery of a new dwarf planet is a bigger deal than it seems. Tens of thousands of new celestial objects are discovered each year, and the Rubin Observatory alone has submitted 11,000 new asteroid discoveries since it started scanning the skies in June 2025. 

If ED138 becomes a dwarf planet, it’ll join just five other such celestial objects with that distinction. They include Eris, Ceres, Haumea, Makemake and Pluto, which was downgraded to a dwarf planet 20 years ago. 

Part of the reason for that is the strict definition of a dwarf planet. It has to be big enough to shape itself into a sphere with the force of its own gravity, orbit the sun and not be a moon. Another important distinction is that dwarf planets have not cleared their orbits of debris, which means they share their orbits with untold numbers of asteroids, comets and other space debris. 

That last distinction is important because regular planets are considered to have cleared their orbits, either by absorbing the debris, sending it away through gravitational interactions or pulling it into stable orbits, as Earth did with the moon.

In short, a regular planet has enough gravitational pull to clear out the space around it, whereas dwarf planets do not. 

The other reason why this would only be the sixth dwarf planet ever discovered is that there’s a lot of stuff in space and researchers often simply don’t know where to look. ED138 orbits in such a spot where it’s backdropped by the Milky Way, a region of space crowded with millions of stars. Thus, it’s very likely that ED138 had been observed by a telescope before but simply got lost in all the background noise. 

Holman says that if Rubin can find this one, it can find others as well, so ED138 may not be the observatory’s last such discovery.

“Rubin is giving us an unprecedented capacity to explore the sky through a combination of speed, depth, and precision,” Mario Jurić, Rubin Solar System Operations team member, said in a statement. “And the discovery is just the beginning: once we identify a new object, we can search back months, and sometimes even decades, finding it in images where nobody knew to look.”

Joe is a freelance journalist. It all started with a long-running affection for building his own PCs, which he did for the first time as a teenager. It evolved into a lifelong enjoyment of putting words on the internet about the subject. He’s written for CNET, PCMag, Mashable and SlashGear as a freelance writer, and worked as a Senior Editor at Android Authority for 10 years. When he’s not writing about tech and science, he’s learning the ins and outs of DIY home repair, gaming, playing his bass guitars and posting help on PC building and gaming subreddits. He is a staunch believer that orange juice should have pulp.

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