Solar System

Geocentric = Earth (geo) is center of universe

Heliocentric = Sun (helio) is center of universe

Which is correct?

Heliocentric… proved by Copernicus and Galileo.

Solar Nebula Theory

How to make a solar system:

1. Start with nebula = a large cloud of dust and gas.

2. The nebula begins to spin and contract from gravity. This creates a flattened disk.

ie: pizza, skirt on spinning ice skater.

Solar Nebula Theory

3. The middle of the disk reaches high temp. and ignites!

Nuclear Fusion = when lighter elements combine into heavier elements (Hydrogen + Hydrogen = Helium)

4. Voila… a star is formed.

Planet Formation

Dust and rocks begin to clump together… like a snowball = accretion.

Planetesimals = objects size of small moons with gravitational fields.

Differentiation = dense materials sink to form core, light materials float and form crust.

Planets

Definition (2006):

1. Must orbit around the Sun.

2. Enough mass to be a sphere.

3. Cleared the “neighborhood” around its orbit.

Planet Groups

Terrestrial Mercury, Venus, Earth and Mars.

-- Rocky surface-- Small diameter -- High density-- Few moons

Jovian Jupiter, Saturn, Uranus and Neptune.

-- No surface-- Large diameter-- Low density-- Many moons

Pluto

Pluto resides in Kuiper Belt.

In 2005, Eris (same size as Pluto) found in Kuiper Belt.

Pluto does not clear out its orbit

Kuiper Belt

Region located 30 to 55 AU (past Neptune).

1,300 objects discovered so far.

May have over a trillion comets and 200 dwarf planets.

Elliptical OrbitsAll planet have elliptical (oval) orbits.

Eccentricity = how flat

1. Two fixed points within ellipse (foci)2. Sun is at one of the foci.

Circle = 0 eccentricityLine = 1 eccentricity

Gravity

Aristotle = heavy objects fall faster than light objects.

Kepler = laws of planetary motion (didn’t know cause).

Galileo = first to test “how objects fall” (didn’t know cause).

Isaac Newton

Gravity is a force.

From Galileo’s ideas he determines that the moon is falling into Earth, but keeps missing it (orbit).

Thought experiment – gravity cannon.

Asteroids

Rocky and Metallic objects that orbit the sun.

Most located between Mars and Jupiter.

Periodically destroy all life on Earth.

Comets

Ball of dust and ice that revolves around the sun.

“Dirty snowball”.

Most come from Kuiper Belt and Oort Cloud… very far from Sun.

Exoplanet

Exoplanet = planet orbiting another star.

Over 1,075 confirmed so far.

First rocky planet found.