Celestial Objects

Pluto

Dwarf Planet

Citation Formats

General Reference

Space and Astronomy Atlas. "Pluto." Accessed August 30, 2026. https://space.interactiveatlas.org/celestial-objects/pluto.

APA Style

Space and Astronomy Atlas. (n.d.). Pluto. Retrieved August 30, 2026, from https://space.interactiveatlas.org/celestial-objects/pluto

BibTeX

@misc{spaceandastronomyatlas-pluto,
  author = {Space and Astronomy Atlas},
  title = {Pluto},
  year = {2026},
  url = {https://space.interactiveatlas.org/celestial-objects/pluto},
  note = {Accessed August 30, 2026}
}

A dwarf planet in the Kuiper Belt, discovered by Clyde Tombaugh. Pluto was classified as the solar system's ninth planet from 1930 until 2006, when the International Astronomical Union adopted a new formal definition of "planet" that Pluto does not meet, reclassifying it as a dwarf planet; the decision remains debated among some astronomers and the public.

Facts

Diameter (km)

2377 1

Mass

1.30 x 10^22 kg 1

Orbital Distance

39.5 AU average (about 5.91 billion km) from the Sun, on an eccentric orbit 1

Discovery Year

1930 2

Disputed

Object Type

Dwarf planet (IAU classification, 2006); planet (1930-2006 classification) 1

Classified as the ninth planet 1930-2006; reclassified as a dwarf planet by the IAU's 2006 definition, a decision some astronomers and the New Horizons mission team have publicly disputed on scientific grounds.

Cross-Tradition Connections

Associated With

Ceres

Why this is disputed. Both bodies were reclassified as dwarf planets under the IAU's 2006 dynamical definition of planet, a classification a minority of planetary scientists dispute in favor of a geophysical definition; see the recorded dissent on Ceres's object-type.

Source Wikipedia (space and spaceflight articles)

New Horizons

Performed the first close flyby of Pluto, in July 2015.

Source NASA Solar System Exploration

New Horizons Mission

Pluto was the mission's primary flyby target, reached on 14 July 2015.

Source Wikipedia (space and spaceflight articles)