Harvard Astronomers Identify Candidate for Eighth Dwarf Planet

Harvard University astronomers have identified a potential new dwarf planet in our solar system, an object estimated to measure between 600 and 1,500 kilometers in diameter. This candidate is one of the brightest objects detected in the solar system in several decades. The discovery was announced Tuesday at the 59th annual meeting of the American Astronomical Society’s Division for Planetary Sciences in Spokane, Washington.

The object, temporarily designated 2026 ED138, ranks among the seven largest bodies identified in the outer regions of the solar system. Matthew Holman, an astrophysicist at the Smithsonian Astrophysical Observatory and a professor at Harvard, explained that the team does not yet know the exact size of the body. He noted that they can only measure the amount of light reaching Earth from the object. This limitation means the body could be smaller with a highly reflective surface, or larger and very dark.

Holman stated that the object is bright enough for amateur astronomers with high-quality equipment to potentially spot it. He described the find as evidence that there are still undiscovered treasures within the solar system. The researchers used the Vera C. Rubin Observatory to make the discovery. Holman described the telescope’s eight-meter mirror as one of the largest in the world, allowing it to capture large amounts of light in short periods and observe faint objects.

The Rubin Observatory features a wide field of view that allows it to scan the entire visible sky from its location in Chile every three nights. Kevin Napier, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, explained that the team identifies moving objects by connecting data points over time. Once enough points are collected, the team can calculate the object’s approximate orbit around the Sun.

Scientists say the object remained undetected because it is located in one of the brightest regions of the night sky, the galactic plane of the Milky Way. This background light made the object difficult to distinguish despite its own brightness. The category of dwarf planet was established in the early 2000s after several new Pluto-sized objects were identified, leading to Pluto’s reclassification. Dwarf planets orbit the Sun and are smaller than traditional planets but possess enough mass for their own gravity to pull them into a spherical shape.

The new candidate joins thousands of known objects in the Kuiper Belt, a region beyond Neptune. Napier noted that many known dwarf planets are currently at their closest points to Earth in their orbits. However, many of these bodies travel to regions three times as far from the Sun as Neptune or farther. At those distances, the objects appear much fainter. Napier said that deeper observations of the night sky will reveal more interesting objects.

Holman said that more images from telescopes are needed to confirm the size of the newly discovered object. He stated that once the size is known, scientists can determine with greater clarity whether it officially qualifies as a dwarf planet. The Vera C. Rubin Observatory will feature in the upcoming NOVA documentary titled Universe in Motion, which is scheduled to premiere on December 16.