Unit 1 Notes: The Solar System and Earth’s Movement
I.
Key Vocabulary
a. Ellipse: oval or flattened circle; the shape of the path that planets follow around the sun
b. Solar System: includes the sun and all the objects that orbit the sun
c. Planet: large round or nearly round body that revolves around the sun and has cleared a
path within its own orbit
II.
a.
b.
c.
d.
e.
f.
g.
h.
Ancient Astronomers
Believed that sun, moon, planets & stars moved around Earth
This is called the geo-centric or earth-centered model of the solar system
Ptolemy (scientist) thought planets moved around Earth in small circles
Nicholas Copernicus developed the sun-centered or heliocentric model of solar system in
1543
Copernicus believed that the planets, moon, & stars moved around the sun
Galileo Galilei observed with telescope the heliocentric model
Tycho Brahe studied positions of planets in late 1500s
Johannes Kepler continued Brahe’s work and found that the orbits of planets were
ellipses
III.
Today’s Solar System
th
a. 8 planets make up the solar system
b. Pluto has become a dwarf planet
c. Pluto was considered a planet for 76 years
d. Because Pluto had not cleared a path within its own orbit it could not be considered a
planet
e. No other solar bodies are in the orbit of planets
f. Sun’s gravitational attraction keeps the planets in orbits shaped like ellipses
g. Small in comparison to whole universe
h. Located in one of the arms of the Milky Way
IV.
Planets
a. Inner planets: Mercury, Venus, Earth, & Mars; made of rock—terrestrial planets
b. Outer planets: Jupiter, Saturn, Uranus, & Neptune; larger than inner planets, made mostly
of gases- “gas giant” planets
V.
Sun
a. One of billions of stars in our galaxy—Milky Way
b. Galaxy is group of many stars held together by gravity
c. Milky Way looks like a pinwheel or spiral with arms
VI.
Other Objects in Solar System
a. Asteroids are small rocky objects orbiting sun
b. Most are in “asteroid belt” between Mars & Jupiter
EE: SRA 68B
JWoods
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