Harvard team identifies potential new dwarf planet in Kuiper Belt

Harvard University astrophysicists have identified a candidate for a new dwarf planet in the outer solar system.

The object, provisionally named 2026 ED138, is estimated to measure between 600 and 1,500 kilometers in diameter. Researchers describe it as one of the brightest objects detected in the solar system in decades. Matthew Holman, an astrophysicist at the Smithsonian Astrophysical Observatory and a professor at Harvard, noted that the team does not yet know the exact size. He explained that they can only measure the amount of light reaching Earth. Consequently, the object could be smaller with a highly reflective surface or larger with a dark surface.

The discovery was announced on Tuesday during the 59th annual meeting of the Division for Planetary Sciences of the American Astronomical Society. The conference is currently taking place in Spokane, Washington. Scientists state that 2026 ED138 ranks among the seven largest objects identified in the outer regions of the solar system. The classification of dwarf planet was adopted in the early 2000s after several Pluto-sized objects were discovered. That finding led to the reclassification of Pluto. By definition, dwarf planets orbit the Sun and are smaller than major planets, but they possess enough mass for their gravity to form a spherical shape.

The object remained undetected for years because it is located in one of the brightest areas of the night sky. It sits within the band of the Milky Way galaxy. This dense star field made it difficult to distinguish the object despite its brightness. Holman stated that the body is bright enough for amateur astronomers with high-quality equipment to observe it. He added that this suggests there are still undiscovered bodies in the solar system.

The team used the Vera C. Rubin Observatory in Chile to locate the candidate. The telescope features an eight-meter mirror, one of the largest in the world. This size allows the instrument to capture large amounts of light in short periods. The observatory also has a wide field of view. It can scan the entire visible sky from its location in Chile every three nights. Kevin Napier, an astrophysicist at the Center for Astrophysics, described the process as connecting the dots of moving objects. Once enough points are tracked, scientists can calculate the object's approximate orbit around the Sun.

The Vera C. Rubin Observatory will feature in the upcoming NOVA documentary Universe in Motion. The film is scheduled to premiere on December 16. The new candidate joins thousands of known objects in the Kuiper Belt, a region beyond Neptune. Scientists believe more objects of this type likely exist. Napier noted that for decades, objects have been hidden in the galactic center region. He compared the search to a game of Where's Waldo. He said the new technology allows astronomers to see and find these hidden items.

Most dwarf planets discovered to date were found at the point in their orbit closest to Earth. However, many travel to much farther regions. Napier explained that some objects reach distances three times greater than the distance to Neptune. These distant bodies appear much fainter. Therefore, deeper observations of the night sky will reveal more interesting objects. Holman said the team needs more telescope images to confirm the size of the new discovery. He stated that knowing the true size will clarify whether the object qualifies as a dwarf planet.