planetoid

plural planetoids

1. datedastronomyAn asteroid of any size

   Numbering of the Planetoids or Asteroidal Planets.—In numbering the planetoids a difficulty has arisen [...]

   1859, J.D. & E.S. Dana, The American journal of science, page 153

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   The group of small bodies that circle round the Sun, outside the orbit of Mars, are known under the designation of the planetoids.

   1856, Robert James Mann, A guide to astromomical science, page 231

   if one can argue for the early existence of a few largely molten planetoids with dimension of kilometers or tens of kilometers, one can quite as easily argue for very large numbers of such planetoids.

   1979, H.A. Zook, “On a New Model for the Generation of Chondrites”, in Lunar and Planetary Science, volume xii, page 1242

2. datedastronomyAn asteroid-like body in an orbit beyond the asteroid belt, such as a centaur or Kuiper belt object
3. astronomyA larger, planetary, body in orbit around the Sun, such as Vesta or (candidate) dwarf planets such Eris or Sedna

   Eris [...] was the upstart planetoid that knocked Pluto off the planetary lists

   2009, Patricia Daniels, Robert Burnham, The New Solar System: Ice Worlds, Moons, and Planets Redefined, National Geographic Books, page 173

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   After discovering "planetoids", bodies orbiting the Sun, even larger than Pluto's moon Charon ... the question of how Sedna and other planetoids came to be.

   2009, Paul A. Czysz, Claudio Bruno, Future Spacecraft Propulsion Systems, pages 377–378

4. astronomyAny planetary body, including classical planets and moons: a planetary-mass object

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   Plate tectonics is a style of convection for an active planetoid where lid fragment (plate) motions reflect sinking of dense lithosphere in subduction zones […] In 2015 humanity completed a 50+ year effort to survey the 30 largest planets, asteroids, satellites, and inner Kuiper Belt objects, which we informally call “planetoids”.

   2018 January 28, Stern, Gerya & Tackley, “Stagnant lid tectonics: Perspectives from silicate planets, dwarf planets, large moons, and large asteroids”, in Geoscience Frontiers, volume 9, number 1, pages 103-119

5. astronomyA dwarf planet

   A dwarf planet or a planetoid is a celestial body that [...]

   2007, Hannu Karttunen et al., editors, Fundamental Astronomy, 5th edition, page 131

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   We prefer the word "planetoid" as a new word to describe round objects orbiting the sun.

   2006, Mike Brown, “Sedna”, in (Please provide the book title or journal name)

   'Dwarf planet' is a dumb phrase. For years we've called things like Pluto and Xena 'planetoids'—planetlike.

   2010, Mike Brown, How I Killed Pluto and Why It Had It Coming, page 223