Quick answer: 2026 ED138 is a large icy trans-Neptunian object, about 46 au from the Sun, that the NSF–DOE Vera C. Rubin Observatory in Chile has found. It is a candidate dwarf planet. The IAU Minor Planet Center announced it on 27 October 2026. Its estimated size is 600–1,500 km. If it is confirmed, it would join Ceres, Pluto, Haumea, Makemake and Eris as the sixth dwarf planet the IAU recognises.
Why 2026 ED138 is in the news
The International Astronomical Union’s Minor Planet Center (MPC) announced the discovery on 27 October 2026 in a Minor Planet Electronic Circular. The same day, Rubin Solar System Lead Scientist Mario Jurić (University of Washington) and Matthew Holman (Center for Astrophysics, Harvard & Smithsonian) presented it at the 58th annual meeting of the American Astronomical Society’s Division for Planetary Sciences in Spokane, USA. It is the first dwarf-planet candidate Rubin has found.
On the evening of 13 October, Holman spotted the object while running Rubin data through a search code he built with Kevin Napier. A later search found that Rubin’s Simonyi Survey Telescope had recorded the object 30 times over 20 nights between 4 March and 11 July 2026. Older images from the Dark Energy Camera (DECam) in Chile go back to 2016, so the team could trace more than ten years of its orbit.
Key facts about 2026 ED138
- Type: A trans-Neptunian object (TNO), meaning it orbits the Sun farther out than Neptune.
- Distance: About 46 au from the Sun at present. Pluto’s average distance is about 40 au. One au is the average distance between the Earth and the Sun.
- Size: 600–1,500 km, estimated from its brightness, distance and assumed albedo (how much light its surface reflects). Infrared observations are needed to narrow this down.
- Orbit: Tilted almost 25° to the plane of the Solar System, which makes it a “hot classical” TNO. This suggests Neptune’s gravity pushed it out of its original orbit.
- Observatory: The Vera C. Rubin Observatory on Cerro Pachón, Chile, funded by the US National Science Foundation and Department of Energy. Its 10-year Legacy Survey of Space and Time (LSST) started in June 2026.
IAU 2006 definitions: planet vs dwarf planet
| Condition | Planet | Dwarf planet |
|---|---|---|
| Orbits the Sun | Yes | Yes |
| Massive enough for gravity to make it nearly round | Yes | Yes |
| Has cleared its orbital neighbourhood | Yes | No |
| Is not a satellite (moon) | — | Yes |
Pluto failed the third test, so the IAU moved it to the dwarf-planet category in 2006. The finding of Eris, which is close to Pluto in size, had triggered that debate.
The five recognised dwarf planets
| Dwarf planet | Region | Discovery | Exam-worthy fact |
|---|---|---|---|
| Ceres | Main asteroid belt (Mars–Jupiter) | 1801, Giuseppe Piazzi | The only dwarf planet in the inner Solar System. NASA’s Dawn mission visited it. |
| Pluto | Kuiper Belt | 1930, Clyde Tombaugh | In 3:2 resonance with Neptune. New Horizons flew past it in July 2015. |
| Haumea | Kuiper Belt | Observations from 2003–04 (two teams claim it) | Spins so fast that it is shaped like an elongated football. About 1,740 km across at the equator. |
| Makemake | Kuiper Belt | March 2005, Mike Brown’s team (Palomar) | Second-brightest Kuiper Belt object after Pluto. About 1,430 km across. |
| Eris | Scattered disc, beyond the main Kuiper Belt | 5 January 2005 (Brown, Trujillo, Rabinowitz) | Slightly more massive than Pluto. About 2,400 km across. Its moon is Dysnomia. |
Kuiper Belt vs Oort Cloud
| Feature | Kuiper Belt | Oort Cloud |
|---|---|---|
| Shape | A thick, doughnut-shaped disc | A spherical shell around the whole Solar System |
| Distance | About 30–50 au. The scattered disc extends to nearly 1,000 au. | Inner edge about 2,000–5,000 au, outer edge about 10,000–100,000 au |
| Comets it supplies | Short-period (Jupiter-family) comets | Long-period comets that arrive from all directions |
| Status | Directly observed. More than 2,000 TNOs are catalogued. | Theorised. It has not been directly observed. |
Exam angle: how NDA, CDS and CAPF can ask this
- NDA general-science papers regularly ask about the IAU criteria and why Pluto lost its planet status.
- Matching each dwarf planet to its region (Ceres in the asteroid belt, the others beyond Neptune) is a common question.
- Questions on comet sources contrast the Kuiper Belt (short-period comets) with the Oort Cloud (long-period comets).
Practice MCQs
Q1. Which IAU condition does a dwarf planet fail to meet?
(a) Orbiting the Sun (b) Being nearly round (c) Clearing its orbital neighbourhood (d) Having a moon
Answer: (c) — dwarf planets have not cleared their orbital zone.
Q2. The only dwarf planet in the inner Solar System is
(a) Eris (b) Ceres (c) Makemake (d) Haumea
Answer: (b) — Ceres lies in the main asteroid belt.
Q3. 2026 ED138 was discovered using data from
(a) the James Webb Space Telescope (b) the Vera C. Rubin Observatory (c) the Hubble Space Telescope (d) the Arecibo Observatory
Answer: (b) — Rubin’s Simonyi Survey Telescope in Chile.
Q4. Long-period comets are mainly thought to come from
(a) the asteroid belt (b) the Kuiper Belt (c) the Oort Cloud (d) Saturn’s rings
Answer: (c) — the distant spherical Oort Cloud.
Frequently asked questions
Is 2026 ED138 officially a dwarf planet?
Not yet. It is a candidate. Infrared observations are needed to confirm its size and whether it is round.
How far away is 2026 ED138?
About 46 au from the Sun, which is farther out than Pluto’s average distance of about 40 au.
How many dwarf planets does the IAU recognise?
Five: Ceres, Pluto, Haumea, Makemake and Eris. If confirmed, ED138 would be the sixth.
Who discovered 2026 ED138?
Matthew Holman of the Center for Astrophysics, Harvard & Smithsonian, using Rubin Observatory data and a search code built with Kevin Napier.
Also read on NCA: ISRO’s next-decade missions | Aditya-L1 and Proba-3 | Monthly defence current affairs PDFs | NDA coaching in Chandigarh
Sources: NSF–DOE Vera C. Rubin Observatory, NASA: Dwarf Planets, NASA: Kuiper Belt, NASA: Oort Cloud, NASA JPL on Ceres. Facts as reported up to 1 November 2026.
Featured image background: NASA/Johns Hopkins University Applied Physics Laboratory/Sou / Wikimedia Commons, Public domain.
