Astronomers have unveiled the detection of a colossal dwarf planet candidate situated deep within the outer margins of our solar system. Spanning an estimated 370 to 930 miles (600 to 1,500 kilometers) across, the celestial body — cataloged temporarily as 2026 ED138 — stands poised to enter the upper tier of dwarf planets located past Pluto’s orbit, pending official verification.

This newly isolated body ranks among the most luminous and expansive trans-Neptunian objects ever logged in the solar system's periphery, courtesy of cutting-edge surveys conducted by the Rubin Observatory in Chile.

By definition, a dwarf planet is a compact planetary-mass body in direct solar orbit that falls short of the physical scale of the classic eight planets. Should ED138 pass all criteria, it will join an elite roster of recognized distant dwarf worlds, sitting alongside Pluto, Eris, Haumea, and Makemake.

New Dwarf Planet Candidate Discovered Beyond Pluto

The groundbreaking find is credited to astronomer Matthew Holman from the Center for Astrophysics | Harvard & Smithsonian. Holman spotted the anomaly while parsing through observational data gathered by the Rubin Observatory earlier this year. On October 13, Holman deployed bespoke software programmed alongside associate Kevin Napier to comb through billions of space detections in search of uncatalogued moving bodies. The computational tool flagged ED138, whose striking luminosity and remote position immediately drew Holman's sharp focus.

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

Subsequent reviews solidified the find, with researchers later spotting ED138 tucked inside archival frames shot by the Dark Energy Camera as far back as 2016.

2026 ED138: Key Facts at a Glance

  • Source: NSF–DOE Vera C. Rubin Observatory
  • Date of Announcement: October 27, 2026

How Large Is Dwarf Planet Candidate 2026 ED138?

To gauge its true scale against celestial neighbors like Pluto, researchers evaluated its optical brightness, orbital distance, and projected surface albedo. These calculations place ED138 between 600 and 1,500 kilometers in diameter. It has the potential to rank as the fourth largest dwarf planet, overshadowing Pluto, Eris, and Haumea, though trailing behind Makemake, Gonggong, Quaoar, and Sedna.

Because of its immense proportions, ED138 is presumed to possess a rounded, spherical shape—a vital benchmark for transitioning from a standard trans-Neptunian object to a classified dwarf planet. Even so, forthcoming infrared evaluations will be essential to pin down exact measurements. At present, ED138 cruises approximately 46 astronomical units (AU) away from the sun, comfortably past Pluto’s average threshold of 40 AU, with an orbital tilt resting at roughly 25 degrees relative to the primary plane of the solar system.

Rubin Observatory Could Discover More Dwarf Planets

Equipped with a record-breaking 3,200-megapixel digital camera, the Rubin Observatory commenced active scientific operations in July. The facility is driving one of the most comprehensive astronomical initiatives ever attempted: a decade-long time-lapse survey of the southern skies. This massive undertaking will yield two million distinct images and 30 trillion individual metrics tracking countless galaxies, stars, and asteroids. Sophisticated scanning logic allows the platform to isolate faint, shifting targets amidst dense fields of background stars.

Earlier in 2026, the Rubin team cataloged upwards of 11,000 fresh asteroid detections, which included roughly 380 unique trans-Neptunian objects.

Rubin will image the whole southern sky again and again for 10 years, so any others hiding in the places earlier surveys skipped are now within reach, noted Holman.

Global astronomy teams are now mobilizing follow-up observation campaigns to dissect ED138’s distinct structural traits and settle whether it earns official classification as a dwarf planet.