Thought Question What does the solar system look like as a whole? Why does the solar system look the way it does? Can we explain how the solar system first formed?

In studying the solar system… We look for patterns amongst the planets. We look for characteristics that the planets share. We look characteristics that they do NOT share. Can we explain these similarities and differences?

Rocky surface, iron, nickel interiors Planet Comparisons Property Terrestrial Planets Jovian Planets Distance from Sun Close Far Mass Small Large Size Composition Rocky surface, iron, nickel interiors Gaseous (H & He) Moons Few Many Rings None Yes Density High Low

Planet Comparisons Distance from Sun Mass Size Composition Moons Rings Property Terrestrial Planets Jovian Planets Distance from Sun Mass Size Composition Moons Rings Density

Terrestrial Planet Comparisons Property Similarities Differences atmospheres composition of atmosphere composition of surface structures cratering temperatures

Jovian Planet Comparisons Property Similarities Differences composition of atmosphere atmospheric storms and winds rings moons Appearance of planet

How are the planets classified? Terrestrial: Mercury, Venus, Earth, Mars Jovian: Jupiter, Saturn, Uranus, Neptune

The Origin of the Solar System should explain… 1. Motion of the planets Planets orbit in the same direction... ...in nearly the same plane... ...in nearly circular orbits. Most planets rotate in the same direction. Most moons orbit in the same direction. 2. Categorizing Planets Planets are either rocky or gaseous.

The Origin of the Solar System should explain… 3. Asteroids and Comets Most asteroids are found between Mars and Jupiter. Most comets have highly elliptical orbits. 4. Age of solar system Common age of rock samples, asteroids, meteorites (4.5 billion years). Common cratering age of ~3.8 billion years 5. Exceptions to the Rules What about Pluto’s elliptical orbit and composition? What about the odd rotation of Venus and Uranus?

Formation of the Solar System We look for a simple, logical, physical explanation for the similarities and differences we see in the planets. We look for a framework that fits with observations—A THEORY! The solar system formed from a cloud of gas and dust in a process known as accretion.

We see evidence of accretion disk around other stars. Q: What is another reason we believe the solar system formed this way? A: ….because we see it happening elsewhere! We see evidence of accretion disk around other stars. For example, this accretion disk around the star b Pictoris.