A planet is generally considered to be a relatively large mass of accreted matter in orbit around a star. A mass that becomes massive enough to undergo nuclear reactions is considered a star, not a planet. The name comes from the Greek term πλανήτης, planētēs, meaning "wanderer", as ancient astronomers noted how certain lights moved across the sky in relation to the other stars. Based on historical consensus, the International Astronomical Union (IAU) lists nine planets in our solar system. However, since the term "planet" has no precise scientific definition, many astronomers contest that figure. Some say it should be lowered to eight by removing Pluto from the list, while others claim it should be raised to ten or even higher depending on how planets are categorized.

Planetary formation

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It is not known with certainty how planets are formed. The prevailing theory is that they are formed from those remnants of a nebula that do not condense under gravity to form a protostar. Instead, these remnants become a thin disc of dust and gas revolving around the protostar and begin to condense about local concentrations of mass within the disc. These concentrations become ever more dense until they collapse inward under gravity to form protoplanets. When the protostar has grown such that it ignites to form a star, its solar wind blows away most of the disc's remaining material. Thereafter there still may be many protoplanets orbiting the star or each other, but over time many will collide, either to form a single larger planet or release material for other larger protoplanets or planets to absorb. Meanwhile, protoplanets that have avoided collisions may become moons of larger planets.

With the discovery and observation of planetary systems around stars other than our own, it is becoming possible to elaborate, revise or even replace this account.

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Forbidden Planet, The - Twitter Search

@KelleyMarie182 Singin' in the Rain; no doubt about that one. Forbidden Planet is a close second, though.
BovinePublic (Samantha Szulhan) Wed, 16 Dec 2009 07:28:54 -0000
@KelleyMarie182 Singin' in the Rain; no doubt about that one. Forbidden Planet is a close second, though.
@uschles Yeah, but I'm way low on my geek input for the week :) I'd watch Forbidden Planet if it was on :D
ing3nu (Kimberly Unger) Wed, 16 Dec 2009 05:07:11 -0000
@uschles Yeah, but I'm way low on my geek input for the week :) I'd watch Forbidden Planet if it was on :D
Im in the mood for some B movie sci fi... Masters of the Universe?? Barbarella?? Forbidden planet?? Hmmmm.
DazzaField (DARREN J FIELD) Tue, 15 Dec 2009 23:50:59 -0000
Im in the mood for some B movie sci fi... Masters of the Universe?? Barbarella?? Forbidden planet?? Hmmmm.
@jessegeek deffo, my brother did archaeology at Cambridge and loved it- but London has the Forbidden Planet Megastore ;)
Pazozo (Zoë Richardson) Tue, 15 Dec 2009 21:16:36 -0000
@jessegeek deffo, my brother did archaeology at Cambridge and loved it- but London has the Forbidden Planet Megastore ;)
@komikero finally read the Forbidden Planet blog! Thanks, Gerry!
Budjette (Budjette Tan) Tue, 15 Dec 2009 19:50:51 -0000
@komikero finally read the Forbidden Planet blog! Thanks, Gerry!
@usmanimubashir bought them at the forbidden planet store in london.
RajeevMasand (Rajeev Masand) Tue, 15 Dec 2009 18:43:02 -0000
@usmanimubashir bought them at the forbidden planet store in london.

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