Astronomy · Dwarf Planets

Pluto

The most famous dwarf planet, in the Kuiper Belt.

Location: Kuiper Belt, beyond Neptune
Classification: Reclassified as a dwarf planet in 2006 (IAU)
Largest moon: Charon
Explored by: NASA's New Horizons (2015 flyby)

NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute · NASA media (public domain)

Gallery

Faces of Pluto
These images, taken by NASA's New Horizons' Long Range Reconnaissance Imager (LORRI), show four different "faces" of Pluto as it rotates about its axis with a period of 6.4 days.
2015
NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute · NASA media (public domain)
Source archive ↗

From planet to dwarf planet

Pluto was discovered in 1930 and long regarded as the ninth planet. In 2006 the International Astronomical Union adopted a formal definition of 'planet'; Pluto did not meet the criterion of clearing its orbital neighborhood and was reclassified as a dwarf planet.

An icy Kuiper Belt world

Pluto orbits in the Kuiper Belt, a region of icy bodies beyond Neptune. It has a thin atmosphere and a system of moons, the largest of which, Charon, is so big relative to Pluto that the two orbit a point between them.

Seen up close

NASA's New Horizons spacecraft flew past Pluto in 2015, transforming it from a blurry dot into a detailed world with mountains of ice, smooth plains, and a famous heart-shaped region.

Knowledge connections

How this connects across Asteria Star — scientific, cultural, and astrological links are kept separate.

Scientific connections

Part ofSolar System
Parent ofCharon
Associated withNew Horizons Flies Past Pluto

Mission connections

Target ofNew Horizons
Visited byNew Horizons

Member of groupKuiper Belt
In orbital resonance2:3 resonance with Neptune
Has featureSputnik Planitia
Has featureTenzing Montes

Space mission
New Horizons
New Horizons is a NASA space probe launched in 2006 that performed the first close flyby of the dwarf planet Pluto in 2015.

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Fast facts

Location: Kuiper Belt, beyond Neptune
Classification: Reclassified as a dwarf planet in 2006 (IAU)
Largest moon: Charon
Explored by: NASA's New Horizons (2015 flyby)

Key points

Once counted as the ninth planet; reclassified as a dwarf planet in 2006.
A small, icy body in the Kuiper Belt beyond Neptune.
Visited by New Horizons in 2015, revealing surprisingly varied terrain.

Data & provenance

Stable ID: dwarf_planet:pluto
Type: Dwarf planet
Domain: Scientific connections
Relationships: 9
Graph version: 1.0.0

Dataset membership

Dwarf Planets

Open data

In the graph export: graph.json · graph.jsonld

Planned API: GET /api/v0/entities/dwarf_planet:pluto

Scientific quality

Complete

Reviewed2 sourcesv1.0.0

7 of 7 applicable dimensions complete

Description: Complete
Source coverage: Complete
Relationship coverage: Complete
Review coverage: Complete
Citation coverage: Complete
Image coverage: Complete
Timeline coverage: Complete

Scientific entity. Dimensions that cannot apply to this object are excluded rather than counted as gaps. See the evidence framework and authority dashboard.

Provenance & sources

review 2026.1

Asteria Scientific Review Process · verification: sourced · accurate

High evidenceconfirmed
Pluto is a dwarf planet in the Kuiper Belt; under the IAU's 2006 definition (Resolution B5) it is classified as a dwarf planet rather than the ninth planet.
Source: NASA (NSSDCA) — NASA Planetary Fact Sheet · Public domain (US Government work)
- NASA Planetary Fact Sheet, Planetary Fact Sheet
- IAU 2006 General Assembly — Definition of a Planet (Resolution B5) (2006)

Reviewed by the internal Asteria Scientific Review Process — not an external institutional review. See the evidence framework and authority dashboard.

Scientific citations

Real, source-backed references — primary papers first, then datasets and institutional sources. Formatted through the citation engine; nothing is fabricated.

DatasetPluto Fact Sheet

NASA Goddard — NSSDCA

Cite (APA / BibTeX)

NASA Goddard — NSSDCA (n.d.). Pluto Fact Sheet. NASA Goddard — NSSDCA. https://nssdc.gsfc.nasa.gov/planetary/factsheet/plutofact.html

@misc{cite:factsheet-dwarf_planet-pluto,
  title        = {Pluto Fact Sheet},
  organization = {NASA Goddard — NSSDCA},
  year         = {n.d.},
  url          = {https://nssdc.gsfc.nasa.gov/planetary/factsheet/plutofact.html},
  note         = {Physical and orbital parameters for Pluto.}
}

Institutional pagePluto — NASA Solar System Exploration

NASA

Cite (APA / BibTeX)

NASA (n.d.). Pluto — NASA Solar System Exploration. NASA. https://science.nasa.gov/

@misc{cite:nasa-dwarf_planet-pluto,
  title        = {Pluto — NASA Solar System Exploration},
  organization = {NASA},
  year         = {n.d.},
  url          = {https://science.nasa.gov/},
  note         = {NASA overview of Pluto.}
}

Standards referenceIAU 2006 General Assembly — Definition of a Planet (Resolution B5)

2006

International Astronomical Union

Cite (APA / BibTeX)

International Astronomical Union (2006). IAU 2006 General Assembly — Definition of a Planet (Resolution B5). International Astronomical Union. https://www.iau.org/

@misc{cite:iau-planet-definition-2006,
  title        = {IAU 2006 General Assembly — Definition of a Planet (Resolution B5)},
  organization = {International Astronomical Union},
  year         = {2006},
  url          = {https://www.iau.org/},
  note         = {Established the 'dwarf planet' category under which Pluto is classified.}
}

Sources & references

The primary and reference sources this topic draws on.

NASANational Aeronautics and Space Administration
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.
IAUInternational Astronomical Union
Official naming, definitions, constellation boundaries, and astronomical nomenclature.
NASA JPLJet Propulsion Laboratory / Solar System Dynamics
Orbital data, ephemerides, and small-body parameters for planets, asteroids, and comets.

Pluto

Gallery

From planet to dwarf planet

An icy Kuiper Belt world

Seen up close

Knowledge connections

Scientific connections

Mission connections

Related

Eris

Ceres

Neptune

Haumea

New Horizons

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Pluto

Gallery

From planet to dwarf planet

An icy Kuiper Belt world

Seen up close

Knowledge connections

Scientific connections

Mission connections

Related

Related entries

Eris

Ceres

Neptune

Haumea

Related missions

New Horizons

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