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Is Pluto a Planet?. Dr John K. Davies & Dr Suzie Ramsay Howat. UK Astronomy Technology Centre, Royal Observatory, Edinburgh, Scotland. The classical solar system. Planet Uranus imaged from Voyager 2. Planet Neptune from Voyager 2. Percival Lowell.
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Is Pluto a Planet? Dr John K. Davies & Dr Suzie Ramsay Howat UK Astronomy Technology Centre, Royal Observatory, Edinburgh, Scotland
9064 Johndavies. A minor planet • Discovered 1993 • Status: Main belt asteroid • Diameter: about 6km • Brightness: V=17-18 • Composition: Rocky • Dist from Sun 2.1-2.7 AU
243 Ida and Dactyl Ida: Size about 56 km long. Dactyl: Size about 1.5 km.
45 Eugenia and its moon. Eugenia size ~215km Satellite size ~13 km Period ~4.7 days
Interstellar comet (never seen) Comet Orbits Long Period Comet, like Hale-Bopp Short Period Comet.
Comet Ring as predicted by Fred Whipple in 1964, virtually what we today call the Kuiper Belt
According to ‘First Steps to Astronomy and Geography’, Hatchard & Son, London, 1828 there are 11 planets. Mercury, Venus, Earth, Mars, Vesta, Juno, Ceres, Pallas, Jupiter, Saturn and Herschel (Uranus) Sun Ceres Venus Pallas Earth Juno Vesta Mars But 4 of these are no longer in lists of planets published today
Tradition in Astronomy Lunar Sea! Constellations
What makes a planet? • It goes around a star.
Io and the Moon are not planets because they don’t go around a star.
What makes a planet? • It goes around a star. • It does not generate heat internally.
Jupiter is a planet. since it is not heated by nuclear reactions.
What makes a planet? • It goes around a star. • It does not make heat by nuclear reactions. • It is spherical.
So MOST asteroids are not planets since they have not collapsed to spherical shapes.
What makes a planet? • It goes around a star. • It does not make heat by nuclear reactions • It is (more-or-less) spherical. • It is bigger than 1000km in diameter
Is Pluto a Planet? Please raise hands for yes
Or not? Please raise hands for NO
Pluto is a small icy planet Like Neptune’s moon Triton