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Observing the Solar System. Section 20.1. Early Observations. Greek Observations Saw star patterns in the sky travel together (Constellations). Early Observations. Some stars seemed to wander (planets) They were later named by the Romans (Mercury, Venus, Mars, Jupiter, Saturn).
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Observing the Solar System Section 20.1
Early Observations Greek Observations • Saw star patterns in the sky travel together (Constellations)
Early Observations • Some stars seemed to wander (planets) • They were later named by the Romans (Mercury, Venus, Mars, Jupiter, Saturn)
Early Observations • Most Greek astronomers believed that Earth was in the center of a celestial sphere. (geocentric system)
Early Observations Claudius Ptolemy • Earth in center • Planets move on small circle that move on bigger circles • Widely accepted for 1500 years
Early Observations Nicholas Copernicus • Believed in a sun centered system (Heliocentric) • Said the planets moved around the sun in circles in 1543 Mikolaj Kopernik
Early Observations Nicholas Copernicus • He was banned by the Catholic church • Galileo used the telescope to support him (Venus phases, Jupiter’s moons) • He was placed under house arrest Mikolaj Kopernik Galileo
Early Observations Tycho Brahe • Made accurate observation for over 20 years
Early Observations Johannes Kepler • Analyzed Brahe’s observations and found that the path of the orbits were ellipses • Kepler’s 1st Law
Early Observations Johannes Kepler • He found that the speed of orbiting planets is constantly changing • Kepler’s 2nd Law
Early Observations Johannes Kepler • When he compared planets, he found a relationship between how far from the sun they were and the time to make one orbit • Kepler’s 3rd Law
Early Observations Today we know of 8 planets (MVEMJSUN) their moons, and smaller objects that revolve around the sun
What about Pluto? • According to the new definition, a full-fledged planet is an object that orbits the sun and is large enough to have become round due to the force of its own gravity. In addition, a planet has to dominate the neighborhood around its orbit. • Pluto does not dominate its neighborhood Charon is half it size It does not sweep up its neighborhood, there is much debris in its orbit