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Eris (dwarf planet)

Dwarf planet whose discovery redefined the Solar System's planetary lineup.

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Eris (dwarf planet)

ESO/L. Calçada and Nick Risinger (skysurvey.org) · CC BY 4.0

Eris is the most massive dwarf planet in the Solar System and the second-largest by volume.[1] The dwarf planet Eris has one confirmed satellite, Dysnomia, and observations suggest the possible existence of a second, significantly larger moon.[2]

Key facts and history

Under the IAU definition approved on August 24, 2006, Eris, Pluto, and Ceres are classified as dwarf planets.[3] The name was proposed by the Caltech team on September 6, 2006, and assigned on September 13, 2006.[4] Mike Brown's team at Palomar Observatory discovered Eris in January 2005 after re-analyzing images captured on October 21, 2003.[5][6] Because initial observations suggested Eris was larger than Pluto, NASA referred to it as the tenth planet in the Solar System.[3]

This situation prompted the International Astronomical Union to create an official definition for the term "planet" for the first time.[3] Data from a 2010 stellar occultation revealed that Eris has a slightly smaller diameter than Pluto, yet it possesses a greater mass.[7][8] Eris's diameter is 2326 km, and its mass exceeds that of Pluto by 27%.[9]

What the research sources say

A 2006 paper by Brown, Schaller, Roe, and Rabinowitz in The Astrophysical Journal measured Eris's size using the Hubble Space Telescope and found a geometric albedo of 0.96.[10][8] A 2025 paper by Ortiz, Morales, and Gutiérrez in Monthly Notices of the Royal Astronomical Society Letters hypothesized that an 18.85-hour brightness variation could be caused by a large unseen moon roughly 1000 km in diameter.[11][12] A 2020 Icarus study by Holler, Grundy, Buie, and Noll determined that Dysnomia's orbit is non-Keplerian, which implies gravitational perturbations from an unidentified source.[13][14]

References

  1. Wikipedia, "Eris (dwarf planet)" (CC BY-SA 4.0), which cites: "Dwarf Planets", Canadian Space Agency, March 12, 2020 (original not read by us) en.wikipedia.org
  2. Wikipedia, "Eris (dwarf planet)" (CC BY-SA 4.0), which cites: Ortiz, "Analysis of the Gaia DR3 photometry of the dwarf planet Eris", Monthly Notices of the Royal Astronomical Society, p. L37–L42; "AstDys (136199) Eris Ephemerides", Department of Mathematics, University of Pisa, Italy (we also read that source) en.wikipedia.org
  3. Wikipedia, "Eris (dwarf planet)" (CC BY-SA 4.0), which cites: "The IAU draft definition of "planet" and "plutons"", IAU, August 16, 2006 (original not read by us) en.wikipedia.org
  4. Wikipedia, "Eris (dwarf planet)" (CC BY-SA 4.0), which cites: Blue, "2003 UB 313 named Eris", USGS Astrogeology Research Program, September 14, 2006; Brown, "New Planet", web.gps.caltech.edu (original not read by us) en.wikipedia.org
  5. Wikipedia, "Eris (dwarf planet)" (CC BY-SA 4.0), which cites: Williams, "The Dwarf Planet Eris", Universe Today, 2015 (original not read by us) en.wikipedia.org
  6. Wikipedia, "Eris (dwarf planet)" (CC BY-SA 4.0), which cites: Brown, "The discovery of 2003 UB313 Eris, the largest known dwarf planet", California Institute of Technology, Department of Geological Sciences, 2006; "Discovery of a Planetary-sized Object in the Scattered Kuiper Belt", The Astrophysical Journal, 2005, p. L97–L100; Maugh, "His Stellar Discovery Is Eclipsed", Los Angeles Times, October 16, 2005 (we also read that source) en.wikipedia.org
  7. Wikipedia, "Eris (dwarf planet)" (CC BY-SA 4.0), which cites: Brown, "The shadowy hand of Eris", Mike Brown's Planets, 2010; Brown, "How big is Pluto, anyway?", Mike Brown's Planets, December 2023; "How Big Is Pluto? New Horizons Settles Decades-Long Debate", NASA, 2015; Stern, "The Pluto System After New Horizons", Annual Review of Astronomy and Astrophysics, September 2018, p. 357–392 (original not read by us) en.wikipedia.org
  8. Wikipedia, "Eris (dwarf planet)" (CC BY-SA 4.0), which cites: "Direct measurement of the size of 2003 UB313 from the Hubble Space Telescope", The Astrophysical Journal, 2006, p. L61–L63 (we also read that source) en.wikipedia.org
  9. Wikipedia, "Eris (dwarf planet)" (CC BY-SA 4.0), which cites: Sicardy, "Size, density, albedo and atmosphere limit of dwarf planet Eris from a stellar occultation", European Planetary Science Congress Abstracts, 2011, p. 137; Brown, "The Mass of Dwarf Planet Eris", Science, June 15, 2007, p. 1585; "Dwarf Planet Outweighs Pluto", space.com, 2007; "How Big Is Pluto? New Horizons Settles Decades-Long Debate", www.nasa.gov, 2015 (we also read that source) en.wikipedia.org
  10. M. E. Brown, "Direct Measurement of the Size of 2003 UB313 from theHubble Space Telescope", The Astrophysical Journal (2006), doi:10.1086/504843. OpenAlex metadata CC0; paper not read. doi.org
  11. José Luis Ortiz, "Analysis of the Gaia DR3 photometry of the dwarf planet Eris", Monthly Notices of the Royal Astronomical Society Letters (2025), doi:10.1093/mnrasl/slaf005. OpenAlex metadata CC0; paper not read. doi.org
  12. Wikipedia, "Eris (dwarf planet)" (CC BY-SA 4.0), which cites: Ortiz, "Analysis of the Gaia DR3 photometry of the dwarf planet Eris", Monthly Notices of the Royal Astronomical Society, p. L37–L42; Ortiz, "Analysis of the Gaia DR3 photometry of the dwarf planet Eris", Monthly Notices of the Royal Astronomical Society, p. L37–L42; Ortiz, "Analysis of the Gaia DR3 photometry of the dwarf planet Eris", Monthly Notices of the Royal Astronomical Society, p. L37–L42; Ortiz, "Analysis of the Gaia DR3 photometry of the dwarf planet Eris", Monthly Notices of the Royal Astronomical Society, p. L37–L42; Or en.wikipedia.org
  13. Bryan J. Holler, "The Eris/Dysnomia system I: The orbit of Dysnomia", Icarus (2020), doi:10.1016/j.icarus.2020.114130. OpenAlex metadata CC0; paper not read. doi.org
  14. Wikipedia, "Eris (dwarf planet)" (CC BY-SA 4.0), which cites: Holler, "The Eris/Dysnomia system I: The orbit of Dysnomia", Icarus, February 2021; Holler, "The Eris/Dysnomia system I: The orbit of Dysnomia", Icarus, February 2021; Holler, "The Eris/Dysnomia system I: The orbit of Dysnomia", Icarus, February 2021; Brozovic, "Revisiting orbit fits for the Eris-Dysnomia system", Bulletin of the American Astronomical Society, September 2023, p. 503.02 (we also read that source) en.wikipedia.org

Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Eris (dwarf planet) (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.

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Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.

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