Intro to the Solar System

Intro to the Solar System

Models and Background Info

Geocentric Model

• A model of space that put the Earth in the very middle of the stars and other planets

• This was the common belief of ancient Chinese and Greeks and lasted until the 1600s

• Most geocentric models only included the planets that were visible with their telescope

Geocentric Model

• A Greek astronomer named Claudius Ptolemy developed his own version of this

• Ptolemy put the Earth in the middle of the ENTIRE universe

Heliocentric Model

• First proposed by ancient Greek scientist, Aristarchus

• His model claimed the Sun was the fixed center of the universe and not the Earth

• Modern heliocentric models show the Sun as the middle of our solar system (SS), and our SS inside a galaxy

Heliocentric Model

• Nicolaus Copernicus tried to make this model more popular in the mid 1500's

• His model worked out the arrangement of the known planets and how they moved around the Sun

Heliocentric Model

• Later on in the 1500's two astronomers, Tycho Brahe and Johannes Kepler, made more accurate observations and calculations

• They discovered the planets do not move in perfect circles, but instead in an ellipse, or an oval shape

Multiple Choice

Which model of the solar system puts the Earth in the middle of everything?

• Heliocentric

• Astrological

• Geocentric

• Copernican

Multiple Select

Who discovered that planets move in an ellipse shape?

• Brahe

• Ptolemy

• Aristarchus

• Kepler

• Copernicus

Our Solar System is VERY large

• So large that it would be insane to measure it by miles, so instead...

• We measure distance in space by Astronomical Units (AU)

• ONE AU is the average distance from Earth to the Sun

• 1 AU = about 150,000,000 kilometers

• Our SS extends to more than 100,000 AU away from the Sun

What's in our Solar System??

• ONE star (the Sun)

• EIGHT planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune)

• FIVE dwarf planets (Pluto, Eris, Ceres, Makemake, Haumea)

• 200+ moons

• and a whole lotta rocks....to be discussed later

Why are some planets called dwarf planets??

• To be considered a "real" planet, it must have THREE characteristics

Planet Criteria

• 1) Be large enough that it is rounded by its own gravity

• 2) It must orbit the Sun

• 3) It must have cleared the path of its orbit

• **Most dwarf planets do not meet #1 or #3

How did the SS form?

• Scientists believe that the solar system formed from a large cloud of hydrogen, helium, rock, ice, and other elements

• This clouds gravity caused it to collapse and pull material towards its center

• The pressure and temperature eventually grew so high that nuclear fusion began and created the Sun

• As the Sun grew, so did it's gravity

• This gravity started pulling together chunks of rock and ice and clouds of gas to form planetesimals

• Eventually these smashed into each other and created all of the planets

Multiple Choice

How many planets are in our SS?

• 7

• 12

• 9

• 8

Multiple Select

Why is Pluto considered a dwarf planet?

• It orbits the Sun

• It does not clear its own orbit

• It has become rounded by its own gravity