2026 ED138: New Kuiper Belt Object Measures Up to 1,500 Kilometers

The search for new bodies in the outer solar system continues to yield results. Astronomers at Harvard University have identified a new object in the Kuiper Belt, a region beyond Neptune that contains thousands of known bodies.

The team estimates the object, provisionally named 2026 ED138, has a diameter between 600 and 1,500 kilometers. This size range places it among the seven largest objects identified in the outer solar system. The announcement took place Tuesday during the 59th annual meeting of the Division for Planetary Sciences of the American Astronomical Society in Spokane, Washington.

Matthew Holman, an astrophysicist at the Smithsonian Astrophysical Observatory and a professor at Harvard, noted that the exact size remains unknown because current data only measures the light reflected from the object. It could be a smaller body with a highly reflective surface or a larger body with a dark surface.

The object had remained undetected despite its brightness because it is located within the dense star field of the Milky Way. This specific region of the night sky is often too bright for standard surveys to easily distinguish moving objects. Holman stated that the body is bright enough for amateur astronomers with high-quality equipment to observe it.

The discovery utilized the Vera C. Rubin Observatory in Chile, a facility equipped with an eight-meter mirror, one of the largest in the world. This hardware allows the telescope to capture significant amounts of light in short periods and scan faint objects. The observatory’s wide field of view enables it to survey the entire visible sky from its location in Chile every three nights.

Kevin Napier, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, explained the method as connecting points of motion. Once enough data points are collected, the team can calculate the object’s orbit around the Sun. Napier noted that many known dwarf planets migrate to regions three times farther from the Sun than Neptune, where they become much fainter.

The category of dwarf planet was formalized in the early 2000s following the identification of several Pluto-sized bodies. These objects orbit the Sun and have enough mass for gravity to give them a spherical shape, though they are smaller than the other planets. The Vera C. Rubin Observatory will feature in the NOVA documentary Universe in Motion, scheduled for release on December 16.

Holman said that additional images are required to confirm the physical size of the new object. Once the dimensions are verified, scientists will be able to determine with greater clarity whether 2026 ED138 meets the criteria for dwarf planet status.