Theory question 203
The Earth and Solar System(a) Describe the solar system. (b) Outline four characteristics each of the following planets: (i) Pluto; (ii) Mercury
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(a) The solar system is the sun and all the bodies that revolve round it: the planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto as counted then) in elliptical orbits, their moons, asteroids (mostly between Mars and Jupiter), comets and meteors; the sun at the centre provides light and heat; planets shine by reflected light; all held by the sun's gravity.
(b)(i) Pluto: farthest from the sun (about 5,900 million km); smallest (about 2,300 km diameter); very cold (about −230°C); longest revolution (about 248 years); has a moon (Charon); highly elliptical orbit; now classed as a dwarf planet.
(ii) Mercury: nearest the sun (about 58 million km); small (about 4,880 km diameter); shortest revolution (88 days); rotates slowly (about 59 days); very hot on the sunlit side and very cold on the dark side; no moon; almost no atmosphere.
Give distance, size, period and temperature for each planet.