Harvard Team Spots Possible New Dwarf Planet With Rubin Telescope

WHO:

WGBH - Harvard University astrophysicists identified a candidate dwarf planet. Matthew Holman is a Smithsonian astrophysicist and Harvard University lecturer; Kevin Napier is an astrophysicist at the Center for Astrophysics at Harvard University and the Smithsonian.

Phys.org - A scientist found the object while examining data from the Simonyi Survey Telescope at the NSF-DOE Vera C. Rubin Observatory.

GeekWire - Rubin Observatory astronomers may find more potential dwarf planets during the observatory’s 10-year sky survey.

WHAT:

ScienceAlert - 2026 ED138’s entire orbit lies within Pluto’s range of distances from the Sun.

ScienceAlert - Further observations, particularly at infrared wavelengths, could help determine ED138’s size and whether it meets the criteria for dwarf-planet status.

ScienceAlert - The hypothetical Planet Nine is one potential target of Rubin’s survey; its existence has been proposed to explain unusual orbits of some distant trans-Neptunian objects.

ScienceAlert - 2026 ED138 may be comparable in size to the dwarf planets Makemake and Haumea.

ScienceAlert - Rubin observations tracked ED138 through 30 detections across 20 nights, from 4 March to 11 July 2026; archival Dark Energy Camera images also recorded it in 2016, 2017, 2018, 2019 and 2023.

ScienceAlert - The Minor Planet Center reports that ED138 takes about 281 years to orbit the Sun, with a perihelion of 36.86 astronomical units and an aphelion of 49.04 astronomical units; its average orbital distance is about 42.95 astronomical units.

ScienceAlert - ED138’s orbit is tilted about 24.5 degrees relative to the plane of the Solar System.

ScienceAlert - Rubin’s 3.2-gigapixel camera can image an area equivalent to about 40 full moons in one exposure.

ScienceAlert - Rubin is expected to discover thousands of previously unknown outer Solar System objects during its decade-long survey.

WGBH - Dwarf planets orbit the Sun and are smaller than planets, but massive enough for their own gravity to make them spherical.

Space.com - If confirmed, 2026 ED138 would be the sixth known dwarf planet in the solar system.

WGBH - The candidate, provisionally named 2026 ED138, is estimated to be 600–1,500 kilometers in diameter and is among the seven largest objects identified so far in the outer solar system. Holman said, “We don’t really know its size because all we can see is how much light we’re getting from it.”

Phys.org - The distant, icy object provisionally named 2026 ED138 orbits beyond Pluto and is a candidate for addition to the solar system’s official dwarf-planet roster.

WGBH - The candidate is among thousands of known objects in the Kuiper Belt, the region beyond Neptune. Additional telescope imaging is needed to establish its size and whether it qualifies as a dwarf planet.

WGBH - The discovery was announced at the 59th Annual Division for Planetary Sciences meeting of the American Astronomical Society. The article says the Vera C. Rubin Observatory will be featured in NOVA’s documentary “Universe in Motion,” premiering Dec. 16.

WHERE:

WGBH - The object was difficult to detect because it lies against one of the night sky’s brightest regions, the Milky Way. The meeting was held in Spokane, Washington; the observatory is in Chile.

WHY:

ScienceAlert - Holman said, “Objects like this are very rare, so I immediately started checking whether I or the code had done something wrong.”

ScienceAlert - Holman said, “My first reaction was one of excited disbelief,” and that he checked whether he or the code had made a mistake because such objects are very rare.

WGBH - Matthew Holman said the candidate is bright enough for capable amateur astronomers to see, adding, “So it sort of demonstrates that we have not found all of the treasures in our solar system yet.”

WGBH - Kevin Napier said many dwarf planets are usually found near the point in their orbits closest to Earth, but can travel three times Neptune’s distance or farther, making them fainter and harder to detect.

WGBH - Holman said the object could be smaller and highly reflective or larger and dark. Its position in the bright Milky Way made it hard to spot despite its brightness.

HOW:

ScienceAlert - Rubin’s survey repeatedly images large areas of the southern sky, allowing astronomers to identify faint objects by tracking changes in their positions against background stars.

WGBH - Researchers used the Vera C. Rubin Observatory’s telescope, which has an eight-meter mirror and a wide field of view. It can survey the entire visible sky from Chile every three nights.

WGBH - Napier described tracking potential moving objects by “play[ing] connect the dots” to estimate their orbits around the Sun. He said deeper observations may reveal fainter, more distant objects.

(UPDATED October 28, 2026 18:00 UTC)

Harvard and Smithsonian astrophysicists have identified 2026 ED138, a distant icy object that could become the sixth known dwarf planet if further observations confirm its size and other characteristics. Its orbit stays within Pluto’s range of distances from the Sun, and estimates suggest it may be comparable in size to Makemake or Haumea, though its diameter remains uncertain. The Vera C. Rubin Observatory found the candidate by repeatedly imaging the sky, and its decade-long survey could uncover thousands more objects in the outer solar system.

(UPDATED October 28, 2026 16:03 UTC)

Astronomers have identified 2026 ED138, a distant, icy object beyond Pluto that could become the solar system’s sixth known dwarf planet if further observations confirm its size and shape. Estimated to be 600 to 1,500 kilometers across, it may be comparable in size to Makemake and Haumea, and it takes about 281 years to orbit the Sun. Researchers spotted it in observations from the Vera C. Rubin Observatory, and its decade-long survey is expected to uncover many more objects in the outer solar system.

(UPDATED October 28, 2026 14:02 UTC)

Harvard University astrophysicists have identified a distant, icy object beyond Pluto that could become the solar system’s sixth known dwarf planet. Provisionally named 2026 ED138, it may be 600 to 1,500 kilometers wide, but more telescope imaging is needed to determine its size and whether it meets the criteria; it was difficult to spot against the bright Milky Way. Researchers found it in data from Chile’s Vera C. Rubin Observatory, whose wide-field telescope scans the visible sky every three nights, and its ongoing survey could reveal more potential dwarf planets.

(UPDATED October 28, 2026 05:01 UTC)

Astronomers have identified 2026 ED138, a distant, icy object beyond Pluto that could become a new dwarf planet, and it ranks among the seven largest objects yet identified in the outer solar system. Researchers spotted it in data from Chile’s Vera C. Rubin Observatory, but its location against the bright Milky Way made it difficult to detect, and more telescope observations are needed to determine its size and whether it qualifies. The object may be 600 to 1,500 kilometers across, though it could be smaller and reflective or larger and dark, and Rubin’s ongoing sky survey could uncover more candidates.