Transcript Slide 1 - Red Hook Central Schools

Formation of the Solar System
Formation of the Solar System
A model of the solar system must explain
the following:
1. All planets orbit the sun counterclockwise
2. All planets orbit in about the same plane
3. Most planetary orbits are nearly circular
4. The distance between the planets
increase in a regular trend with distance
from the sun
5. Most planets orbit counterclockwise with
little axis tilt (<25 degrees)
6. Almost all moons orbit in the same
direction their planet rotates
7. Almost all moons orbit near their planet’s
equatorial plane
8. The sun rotates in the same direction as
the planets orbit (counterclockwise)
Why is solar system so orderly?
2nd challenge: Why two types of
planets?
1. Terrestrial/rocky: Mercury, Venus, Earth,
Mars
Small
2. Jovian/gas giants: Jupiter, Saturn,
Uranus, Neptune
large, Hydrogen-rich,
many moons, rings of rock and ice
3rd Challenge: asteroids and
comets
• Asteroids mostly in asteroid belt between
Mars and Jupiter
• Comets mostly in Kuiper Belt and Oort
cloud
4th challenge: exceptions to the rule
• Mercury has a more eccentric orbit
• Mercury’s orbit is more inclined
• Uranus’ axis of rotation is tilted almost on
its side
• Venus rotates backwards (clockwise)
• Earth has a very large moon
• A few Jovian moons orbit opposite
direction from their planet’s rotation
New stars like our sun, and their planetary systems,
form from the gas and dust remains of older exploded stars.
Flattening of planetary disk
•
•
•
•
explains why:
Planets all rotate in nearly the same plane
Planets all orbit in same direction
Most planets spin in the same direction
Collisions within the disk tend to make
elliptical orbits more circular
Contraction:
Interstellar cloud
contracts due to
gravity
Cloud heats up, spins
Condensation:
Rocks and metals
condense in inner
solar system
H and He gas
collect to make
gas giants
Accretion:
Materials collide
and stick together
Clearing:
Other gases lost to space
Leftovers become asteroids
Comets, Kuiper belt
Explaining the exceptions:
•
•
Jovian planets captured some moons
Giant impacts caused:
1. Earth’s large moon to break off from Earth
2. Backward rotation of Venus
3. Axis tilts of Earth and Uranus