--- title: Dwarf planet candidate appears which takes roughly 280... description: Astronomers have spotted a new object, 2026 ED138, orbiting far beyond Pluto that could become the sixth recognized dwarf planet. It sits 46 times farther from... canonical: https://daily.dev/posts/dwarf-planet-candidate-appears-which-takes-roughly-280-years-to-orbit-our-sun-yuikybzsz twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Dwarf planet candidate appears which takes roughly 280 years to orbit our sun | daily.dev og:description: Astronomers have spotted a new object, 2026 ED138, orbiting far beyond Pluto that could become the sixth recognized dwarf planet. It sits 46 times farther from... og:url: https://daily.dev/posts/dwarf-planet-candidate-appears-which-takes-roughly-280-years-to-orbit-our-sun-yuikybzsz og:image: https://api.daily.dev/og/posts/yUIkyBZsz.png og:image:alt: Dwarf planet candidate appears which takes roughly 280 years to orbit our sun og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Dwarf planet candidate appears which takes roughly 280 years to orbit our sun **[Hacker News](https://daily.dev/sources/hn)** · 6 min read · 0 upvotes · 0 comments ## Summary Astronomers have spotted a new object, 2026 ED138, orbiting far beyond Pluto that could become the sixth recognized dwarf planet. It sits 46 times farther from the sun than Earth and takes 281.1 years to orbit. Size estimates range from 370 to 930 miles across, but confirming it requires infrared observation or watching it pass in front of a star. Matthew Holman and colleagues traced it in data going back to 1937 using the Vera C. Rubin Observatory. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What is 2026 ED138 and could it be a new dwarf planet? 2026 ED138 is a newly identified object orbiting far beyond Pluto, roughly 46 times farther from the sun than Earth, completing one orbit every 281.1 years. Its estimated size ranges from 370 to 930 miles across. Astronomers found it in Vera C. Rubin Observatory data and traced it back in historical images, including photographic plates from 1937, but still need infrared or occultation measurements to confirm its size and classify it as a dwarf planet. _Those tracking space discoveries as they unfold can follow updates on daily.dev._ ### How many dwarf planets are currently recognized in the solar system? Five dwarf planets are currently recognized: Pluto, Eris, Makemake, Haumea, and Ceres. The first four orbit in the distant Kuiper Belt, while Ceres sits in the main asteroid belt between Mars and Jupiter. A sixth candidate, 2026 ED138, has recently been found orbiting far beyond Pluto and may join this group once its size is confirmed. _Space enthusiasts tracking new discoveries can keep up with developments like this on daily.dev._ ### How do astronomers measure the size of a distant object like a dwarf planet candidate? Astronomers use two main methods: observing infrared light to detect thermal energy emitted after solar warming, which reveals approximate temperature and thus size, or watching the object pass in front of a star and measuring how long it blocks the star's light combined with its speed. Brightness alone is insufficient since a small, highly reflective object can appear as bright as a larger, duller one. _Readers curious about observational astronomy techniques can explore more science coverage on daily.dev._ ## Community take How the wider developer community reacted, aggregated from 1 discussion and 121 comments across hackernews (as of 2026-11-13). **TL;DR:** Most of the discussion sidesteps the discovery itself and reignites the long-running argument over whether Pluto-like bodies should count as planets, with sharp disagreement over the IAU's 'dwarf planet' classification; a smaller thread focuses on the technical details of how the object was found and tools to visualize its orbit. **Sentiment:** 15% positive · 25% mixed · 60% skeptical **The case for** - Some argue the dwarf planet category is a useful, scientifically sound classification that reflects real physical differences between objects. - A few praise the discovery method, noting it was found in archival plates back to 1937 and via the new Vera Rubin Observatory's unique capability to spot objects against dense Milky Way starfields. - Several enjoyed and praised a community-built interactive orbit visualization tool shared in the thread. **The pushback** - Many argue the IAU's 2006 'clear the neighborhood' definition is arbitrary, inconsistent, and effectively reverse-engineered to exclude Pluto. - Critics point out the definition doesn't work for exoplanets, creating two incompatible definitions of 'planet'. - Some say the classification debate itself is pointless bikeshedding driven by non-experts rather than substantive science. - Several note the mnemonic/memorization argument for keeping the planet count low is irrelevant to actual science. **By community** - hackernews (heated): The thread is dominated by a long-running, contentious debate over planetary classification and the Pluto 'demotion,' with only a smaller portion engaging directly with the new object's discovery and detection method. **Hottest debate:** Whether Pluto and similar bodies should be considered true planets or a separate 'dwarf planet' category, and whether the IAU's defining criteria are scientifically coherent or arbitrarily reverse-engineered. **Open questions** - Could there be a larger undiscovered Planet X/Nine still hiding in the outer solar system? - Why was this object hidden for so long given it's one of the brightest trans-Neptunian objects found? **Highlights** > Classifications are useful! It is poor form to take a widely used and historic term and add on a whole different (dynamic!!) category of attribute as a filter on the definition. There is quite a bit of absurdity in the 2006 IAU's definition of a planet. If a massive object came into the solar system and perturbed orbits, caused chaos and collisions, then any "planet" with debris within its neighborhood would cease to be a planet. What do we gain from adding a whole different category of attribute (relationship to its neighborhood) as a criterion? Does it realistically outweigh decades or centuries of peoples intuition of the existing definition? Its not just a matter of science, but language and communication. If you want greater specificity, come up with a new term or use compounded terms. It very much seems like the definition was just shoe-horned to stem any more planets needing to be added. It would be interesting to know if astronomers walk the walk when it comes the definition. If I research when planets were formed would I get the date when their neighborhoods were cleared? Do discussions around large events that send debris into the neighborhood of planets correctly reflect that they cease to be planets until it is cleared? Alan Stern said it best >"We're going to call it a cow, except when it's in a herd." A river is a river, independent of whether there are other rivers nearby. In science, we call things what they are based on their attributes, not what they're next to. >And the IAU definition is even worse, because it produces different categorizations for identical objects, depending on where they are. Get this — Earth at the same distance from the sun [as Pluto] would not be a planet by the IAU’s measure, because Earth can’t clear that zone either. I would say any definition that produces a result where Earth is not a planet under any circumstance is immediately indicted as ridiculous, because one thing we all agree is a planet is planet Earth! >That's crazy. No wonder teachers and students are frustrated, confused, unhappy. It reflects poorly on astronomy, to have something so illogical. https://www.space.com/12710-pluto-defender-alan-stern-dwarf-... > — [cookingmyserver on hackernews · 2 comments](https://news.ycombinator.com/item?id=50474804) > Ceres by itself doesn't really challenge Pluto's old classification. Pluto has 14 times the mass of Ceres, and five moons. Ceres is the only "dwarf planet" classified so far that has zero moons. There are still good arguments for a definition that doesn't consider Ceres a dwarf planet. This helps illustrate how arbitrary these classifications are. They depend entirely on what properties are included in the definition. The updated IAU definition is essentially reverse engineered to fit how they wanted to classify the planets. > — [antonvs on hackernews · 2 comments](https://news.ycombinator.com/item?id=50473500) > > Another factor that kept ED138 hidden is that it is on the same plane as our galaxy. “For the last 20 years, the object has kind of been looping its way across the Milky Way, from our point of view,” Holman explained. “People don’t typically search for things in the Milky Way, because there’s so many stars that it’s really hard to find moving objects.” [1] This thing was actually found despite its location, not because of it. If it had been in the opposite part of the sky we almost certainly would have spotted it sooner, given that it's one of the brightest TNOs we've discovered. We're finding it now because Vera Rubin (the instrument that found it) just came online and is exceptionally good at finding these kinds of objects specifically, even when they're hiding amidst a dense population of stationary background stars. [1] https://edition.cnn.com/2026/10/28/science/ed138-dwarf-plane... > — [combobyte on hackernews · 1 comments](https://news.ycombinator.com/item?id=50476356) > If anyone is interested, here is its orbit, my old day job was to compute orbits for asteroids and comets. (This uses wasm, meant for a desktop, and will download the asteroid catalog of about 65mb, you have been warned) https://dahlend.github.io/ketev/#t=2009-07-01.717&sel=2026%2... This is a big boy. > — [ddahlen on hackernews · 6 comments](https://news.ycombinator.com/item?id=50474001) > https://www.washington.edu/news/2026/10/27/rubin-observatory... > ED138 joins the rapidly growing sample of solar system objects discovered by Rubin since it began collecting early data in preparation for the Legacy Survey of Space and Time (LSST), which began in June 2026. In April, before LSST formally began, the Rubin solar system team announced observations of over 11,000 new asteroids, which included roughly 380 new TNOs. At the time, the team called this large submission “the tip of the iceberg” and expressed their excitement for the discoveries to come once LSST began. With the discovery of ED138, those hopes are coming to fruition. My point was that the LSST survey was looking in those areas as part of its "mapping the Milky Way" https://rubinobservatory.org/explore/how-rubin-works/lsst Another recent discovery from Rubin - https://www.washington.edu/news/2026/11/05/rubin-observatory... You can see that it is looking in those dense starfield areas. https://rubinobservatory.org/gallery/collections/news-images... is where Rubin detected 12,700 new asteroids... and ED138 is in that part of the sky where Rubin was looking. Pluto has a 248 year orbit... which is close to the 282 years for ED138. 100 years ago, maybe Tombaugh would have found ED138 that if he was looking in that part of the sky. https://dahlend.github.io/ketev/#t=1930-02-18.717&sel=2026%2... In 1925, ED138 was crossing Pluto's orbit (and closer to Earth than Pluto was). > — [shagie on hackernews](https://news.ycombinator.com/item?id=50478046) **Source threads** - [hackernews](https://news.ycombinator.com/item?id=50472490) · 266 points · 121 comments ## Similar posts on daily.dev - [Astronomers catch a star slowly snacking on a brown dwarf, 300 light years away](https://daily.dev/posts/astronomers-catch-a-star-slowly-snacking-on-a-brown-dwarf-300-light-years-away-tpuamvbux) · MIT News · 0 upvotes · 0 comments - [Earth-like LHS 1140b May Feature The First Atmosphere Found On Exoplanet](https://daily.dev/posts/earth-like-lhs-1140b-may-feature-the-first-atmosphere-found-on-exoplanet-qzzxakukj) · Hackaday · 0 upvotes · 0 comments - [Astronomers discover a brand-new type of astrophysical object: A black hole star](https://daily.dev/posts/astronomers-discover-a-brand-new-type-of-astrophysical-object-a-black-hole-star-6rgfil5ym) · MIT News · 0 upvotes · 0 comments - [What is a light-day? The milestone Voyager 1 is closing in on](https://daily.dev/posts/what-is-a-light-day-the-milestone-voyager-1-is-closing-in-on-rqlknoosq) · Hacker News · 0 upvotes · 0 comments --- [View this post on daily.dev](https://daily.dev/posts/dwarf-planet-candidate-appears-which-takes-roughly-280-years-to-orbit-our-sun-yuikybzsz) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Dwarf planet candidate appears which takes roughly 280 years to orbit our sun","url":"https://daily.dev/posts/dwarf-planet-candidate-appears-which-takes-roughly-280-years-to-orbit-our-sun-yuikybzsz","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/dwarf-planet-candidate-appears-which-takes-roughly-280-years-to-orbit-our-sun-yuikybzsz"},"datePublished":"2026-11-12T20:47:20.788Z","dateModified":"2026-11-13T07:26:42.299Z","description":"Astronomers have spotted a new object, 2026 ED138, orbiting far beyond Pluto that could become the sixth recognized dwarf planet. 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