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What is the difference between planetoid and planet?

planetoid | planet |

Planet is a derived term of planetoid.



In astronomy terms the difference between planetoid and planet

is that planetoid is a dwarf planet while planet is a body which orbits the Sun directly and is massive enough to be in hydrostatic equilibrium (effectively meaning a spheroid) and to dominate its orbit; specifically, the eight major bodies of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. (Pluto was considered a planet until 2006 and has now been reclassified as a dwarf planet..

planetoid

English

Noun

(en noun)
  • (astronomy) An asteroid of any size
  • * {{quote-book
    • , year=1856 , author=Robert James Mann , site= , title=A guide to astromomical science , page=231 , passage=The group of small bodies that circle round the Sun, outside the orbit of Mars, are known under the designation of ''the planetoids .}}
  • * {{quote-journal
    • , year=1859 , author=J.D. & E.S. Dana , site= , title= , journal=The American journal of science , volume= , date= , page=153 , passage=Numbering of the Planetoids''' or Asteroidal Planets.''—In numbering the ' planetoids a difficulty has arisen [...]}}
  • * 1979' ''Tsunami generation by pelagic '''planetoid impact
  • * {{quote-journal
    • , year=1979 , author=H.A. Zook , site= , title=On a New Model for the Generation of Chondrites , journal=Lunar and Planetary Science , volume=xii , date= , page=1242 , passage=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 .}}
  • (astronomy) An asteroid-like body in an orbit beyond the asteroid belt, such as a centaur or Kuiper belt object
  • (astronomy) A larger, planetary, body in orbit around the Sun, such as Vesta or (candidate) dwarf planets such Eris or Sedna
  • * 1991' ''Optimal trajectories for an ion driven spacecraft from earth to the '''planetoid Vesta
  • * {{quote-book
    • , year=2009 , author=Paul A. Czysz, Claudio Bruno , site= , title=Future Spacecraft Propulsion Systems , publisher= , page=377–378 , passage=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.}}
  • * {{quote-book
    • , year=2009 , author=Patricia Daniels, Robert Burnham , site= , title=The New Solar System: Ice Worlds, Moons, and Planets Redefined , publisher=National Geographic Books , page=173 , passage=Eris [...] was the upstart planetoid that knocked Pluto off the planetary lists}}
  • (astronomy) A dwarf planet
  • * {{quote-book
    • , year=2007 , author= , editor=Hannu Karttunen et al. , title=Fundamental Astronomy , edition=5 , publisher= , page=131 , passage=A dwarf planet'' or a ''planetoid is a celestial body that [...] }}
  • * {{quote-book
    • , year=2010 , author=Mike Brown , editor= , title=How I Killed Pluto and Why It Had It Coming , edition= , publisher= , page=223 , passage='Dwarf planet' is a dumb phrase. For years we've called things like Pluto and Xena 'planetoids'—planetlike. }}

    Usage notes

    The term "planetoid" has never been precisely defined. At first, it was a synonym for asteroid; whereas "asteroid" referred to the star-like image seen through a telescope, "planetoid" referred to its planet-like orbit. Though it approached the popularity of "asteroid" ca. 1915, this usage was never dominant, and largely ceased by ca. 1980. Even before then the etymology of the term was reanalyzed as meaning planet-like in form, and started being used for larger asteroids such as Vesta which had planet-like geologies (that is, were planetary bodies). There was an increase in such usage after 2000 with the discovery of planetary bodies in the Kuiper belt and beyond, which many felt were not appropriately called "asteroids" and concomitant with doubts as to the appropriate definition of "planet". Sedna, for example, was called a "planetoid" in its discovery announcement.

    See also

    * planetesimal * minor planet * dwarf planet * planemo

    External links

    * (wikipedia "planetoid") ----

    planet

    English

    (wikipedia planet)

    Noun

    (en noun)
  • *, II.12:
  • *:Be they not dreames of humane vanity,?
  • *1749 , (Henry Fielding), Tom Jones , Folio Society, 1973, p.288:
  • *:The moonbegan to rise from her bed, where she had slumbered away the day, in order to sit up all night. Jones had not travelled far before he paid his compliments to that beautiful planet , and, turning to his companion, asked him if he had ever beheld so delicious an evening?
  • *1971 , , Religion and the Decline of Magic , Folio Society, 2012, p.361:
  • *:Another of Boehme's followers, the Welshman Morgan Llwyd, also believed that the seven planets could be found within man.
  • (lb) A body which orbits the Sun directly and is massive enough to be in hydrostatic equilibrium (effectively meaning a spheroid) and to dominate its orbit; specifically, the eight major bodies of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. (Pluto was considered a planet until 2006 and has now been reclassified as a dwarf planet.)
  • *1640 , (John Wilkins), (title):
  • *:A Discovrse concerning a New Planet'. Tending to prove, That 'tis probable our Earth is one of the ' Planets .
  • *2006 , Alok Jha, The Guardian , 22 December:
  • *:Their decision will force a rewrite of science textbooks because the solar system is now a place with eight planets' and three newly defined "dwarf ' planets "—a new category of object that includes Pluto.
  • A large body which directly orbits any star (or star cluster) but which has not attained nuclear fusion.
  • In phrases such as the planet'', ''this planet , sometimes refers to the Earth.
  • *
  • *:"My tastes," he said, still smiling, "incline me to the garishly sunlit side of this planet ." And, to tease her and arouse her to combat: "I prefer a farandole to a nocturne; I'd rather have a painting than an etching; Mr. Whistler bores me with his monochromatic mud; I don't like dull colours, dull sounds, dull intellects;."
  • *{{quote-magazine, date=2013-06-07, author=David Simpson
    • , volume=188, issue=26, page=36, magazine=(The Guardian Weekly) , title= Fantasy of navigation , passage=It is tempting to speculate about the incentives or compulsions that might explain why anyone would take to the skies in [the] basket [of a balloon]:

    Usage notes

    The term planet'' originally meant any star which wandered across the sky, and generally included comets and the Sun and Moon. With the Copernican revolution, the Earth was recognized as a planet, and the Sun was seen to be fundamentally different. The Galileian satellites of Jupiter were at first called planets (satellite planets), but later reclassified along with the Moon. The first asteroids were also thought to be planets, but were reclassified when it was realized that there were a great many of them, crossing each other's orbits, in a zone where only a single planet had been expected. Likewise, Pluto was found where an outer planet had been expected, but doubts were raised when it turned out to cross Neptune's orbit and to be much smaller than the expectation required. When Eris, an outer body more massive than Pluto, was discovered, the International Astronomical Union (IAU) officially defined the word ''planet as above. However, a significant minority have refused to accept the IAU definition. Many simply continue with the nine planets that had been recognized prior to the discovery of Eris. Others are of the opinion that orbital parameters should be irrelevant, and that any equilibrium (?spherical) body in orbit around a star is a planet; there are likely several hundred such bodies in the Solar system. Still others argue that orbiting a star should also be irrelevant, thus re-accepting the Galileian satellites (as well as a dozen other moons) as planets. Note that the 2006 IAU definition defines a planet in respect to the Sun, and is thus technically inapplicable to exoplanets.

    Synonyms

    * *

    Derived terms

    (terms derived from "planet") * carbon planet * carbide planet * diamond planet * dual planet * dwarf planet * exoplanet * extrasolar planet * free-floating planet * gas giant planet * giant planet * ice giant planet * interstellar planet * inner planet * major planet * mesoplanet * minor planet * outer planet * Planet Earth * planemo * planetar * planetary-mass object * planetary * planetarium * planetesimal * planetoid * planet-ruler * planet-struck * satellite planet * silicate planet * silicon planet * superplanet * supergiant planet * terrestrial planet * water planet

    Related terms

    * gas giant * ice giant * sub-brown dwarf * planetary object

    See also

    * * moon * orbit

    References

    * First Steps to Astronomy and Geography , 1828, (Hatchard & Son: Piccadilly, London).

    Anagrams

    * * ----