Sentence:  `` The human ego being what it is '' , I put in , `` science fiction has always assumed that the creatures on the <WSD>planets</WSD> of a thousand larger solar systems than ours must look like gigantic tube-nosed fruit bats . 
Meaning of the word marked with <WSD> tags:  (astronomy) any of the nine large celestial bodies in the solar system that revolve around the sun and shine by reflected light; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto in order of their proximity to the sun; viewed from the constellation Hercules, all the planets rotate around the sun in a counterclockwise direction