planemo

pla·ne·mo
P3L1A1N1E1M3O1
/ˈplæ.nə.moʊ/

noun

an astronomical object with enough mass to achieve hydrostatic equilibrium, but not enough to initiate core fusion at any time in its existence. That is, it is rounded in shape and is smaller than a star. Planemos include planets, dwarf planets, and the larger moons of the Solar System (satellite planets), but also sub-brown dwarfs and rogue planets between the stars.

Scrabble 11

Meanings

nounplanemo (plural planemos)

plural planemos

  1. astronomyan astronomical object with enough mass to achieve hydrostatic equilibrium, but not enough to initiate core fusion at any time in its existence. That is, it is rounded in shape and is smaller than a star. Planemos include planets, dwarf planets, and the larger moons of the Solar System (satellite planets), but also sub-brown dwarfs and rogue planets between the stars.

    Other groups have also recently identified young, isolated planemos; understanding how such isolated, ultra-low masses form presents a challenge.

    2003 December 1, Jacques Lépine, Jane Gregorio-Hetem, Open Issues in Local Star Formation, page 266

Origin

Contraction of planetary-mass object. Coined by Gibor Basri, Professor of Astronomy at the University of California, Berkeley, (UCB) at the 2003 IAU conference.

Full word history & related roots →

Translations

German Objekt planetarer Masse
  • Objekt planetarer Masseplanemo
Polish planemo
  • planemoplanemo
Turkish planemo
  • planemoplanemo

Rhymes & wordplay

Anagrams

Cite this entry
APA

planemo. (n.d.). In WatkinsX Dictionary. Retrieved November 2, 2026, from https://dictionary.watkinsx.com/word/planemo

MLA

“planemo.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/planemo. Accessed November 2, 2026.

Chicago

WatkinsX Dictionary, s.v. “planemo,” accessed November 2, 2026, https://dictionary.watkinsx.com/word/planemo.

Source: planemo on Wiktionary, CC BY-SA 4.0.