Dwarf planet candidate appears which takes roughly 280 years to orbit our sun

Matthew Holman , a senior astrophysicist at the Smithsonian Astrophysical Observatory, was sifting through data from the Vera C. Rubin Observatory in Chile when something odd caught his eye. Running a custom-made computer program, he and his colleague Kevin Napier had already spotted more than 2,000 little bright dots in the telescope data, corresponding to newly discovered small objects in the distant solar system. But this one was different: It seemed to be big. Holman managed his expectations. After all, astronomers in the business of finding distant objects are used to disappointment. “We all have ‘found Mars’ … in terms of a false positive,” Holman tells Smithsonian magazine. They find a bright object that seems really big, then, with a closer look, learn that it’s nothing very remarkable after all. “We’re all really cautious when you see something that looks like it’s large.” Still, this object grabbed Holman’s attention, so he tried to verify it with Napier and Rubin solar system lead scientist Mario Jurić . They found the celestial body in previous photos of the sky throughout the past decade, which helped them zero in on its orbital path—and the more historical data they found, the more confident they became. “We know that it’s real,” Holman says. “Every time you look at the predicted location, there it is.” They even found it in photographic plates from 1937, stored in the Harvard plate stacks , he says. The object, called 2026 ED138 , is 46 times farther from the sun than Earth is, and it takes 281.1 years to complete an orbit. Now, the central question is whether it’s big enough to be classified as a new dwarf planet, which would put it among the rare ranks of only five other objects in our solar system. “This is incredibly exciting,” Paul Byrne , a planetary scientist at the Washington University in St. Louis who was not involved in the discovery, tells National Geographic ’s Robin George Andrews. “It heralds a new era of solar system and planetary science.” 2026 ED138 3D orbit Watch on Dwarf planets are smaller planets that orbit a star and have a nearly round shape, which happens naturally with objects above a certain size, as their gravitational force pulls evenly on all sides . But dwarf planets are not large enough for their gravity to clear their orbital paths of similar-size debris—the eight planets of our solar system, meanwhile, have achieved that feat. (Pluto’s designation was changed from planet to dwarf planet in 2006 for this reason—its orbit is littered with icy Kuiper Belt objects.) Quick fact: Dynamic dwarf planet Ceres, a dwarf planet in the main asteroid belt between Mars and Jupiter, may contain salty water that can percolate onto the surface in some regions. ED138 is likely big enough to be round and, therefore, a dwarf planet—estimates for its size currently range from 370 miles to 930 miles across. But astronomers will have to confirm that measurement, and from the object’s brightness alone, that’s impossible. A highly reflective, smaller object, perhaps covered in gleaming ice caps, might appear just as bright as a less reflective, duller body that’s much larger. Astronomers have two ways to get the required data. They could observe the world in infrared light, which reveals the thermal energy that it emits after being warmed by the sun. “From that you can figure out how big it is, because we know approximately what temperature it should have,” Holman says. Alternatively, astronomers could watch the dwarf planet candidate pass in front of a star. If they know how much light comes from that star and how fast ED138 is moving, they can calculate the body’s size based on how long it obscures the light. Holman says people are working on making those observations with telescopes such as the Atacama Large Millimeter/submillimeter Array (ALMA). The dwarf planet candidate isn’t extremely easy to see at the moment, he adds, but “in the next few months it will be, and people will try.” Right now, astronomers recognize five dwarf planets: Pluto , Eris , Makemake and Haumea in the distant Kuiper Belt, and Ceres in the main asteroid belt between Mars and Jupiter. Experts have long suspected that there could be more of these objects, but many of them could have highly elliptical orbits that keep them too far away for us to see most of the time. What we observe is potentially the “tip of the iceberg of a few that are in the close part of their orbit,” Holman says. “There must be a lot that we just haven’t yet detected.” The discovery also hints at a relatively unexplored area of our solar system—the region that’s in front of the dense, starry core of the Milky Way from our perspective. It’s harder to pick out objects against all the background light in that zone, and ED138 has been traveling through it for the past 25 to 30 years, Holman notes. “There’s a swath on the sky where we really don’t have a good idea of what is there,” he adds. What’s more, ED138 is in the southern hemisphere’s sky, and a lot of astronomical observations have focused on the northern hemisphere. But Rubin is poised to help change that: The new telescope, which has the world’s largest digital camera and captured its first images last year, is one of several observatories operating out of Chile’s Atacama Desert. “Rubin is giving us an unprecedented capacity to explore the sky through a combination of speed, depth and precision,” Jurić says in a statement . “I was surprised that it found such an object so early,” Megan Schwamb , a planetary scientist at Queen’s University Belfast in Northern Ireland and a member of the Rubin solar system operations team, tells CNN ’s Jacopo Prisco. “This was not on my bingo card for this year.” Understanding more about how and where ED138 formed could reveal new details about the early days of the solar system. And its existence offers a clear reminder that surprising objects remain to be found on the fringes of our planetary neighborhood. “Is there a Mars- or Earth-size or bigger object out there?” Holman says. “That’s not ruled out.” You Might Also Like What Seeded Life on Earth? New Research Challenges the Longstanding Theory That Comets Brought the Ingredients to Our Planet November 12, 2026 A Rare Surviving Letter From Martha Washington Sheds Light on Her Young Daughter's Struggle With Epilepsy November 11, 2026 The Handwritten Final Draft of Martin Luther King Jr.'s 'I Have a Dream' Speech Was Considered Lost. It Turned Out to Be Sitting in a Desk Drawer for Decades November 10, 2026 Octopuses Are the Ultimate Escape Artists. 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