Transcript Observing the Solar System

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)
Mikolaj Kopernik
• Said the planets moved
around the sun in circles in
1543
Early Observations
Nicholas Copernicus
• He was banned by the
Catholic church
Mikolaj Kopernik
• Galileo used the telescope
to support him (Venus
phases, Jupiter’s moons)
• He was placed under house
arrest
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