Formation of Earth Solar System Observations 1 All

Formation of Earth

Solar System - Observations 1. All planets revolve around the sun in the same direction; this direction is the same as the rotation of the sun. 2. The orbits around the sun are nearly circular. 3. All planetary orbits except that of Pluto lie in a common plane, called the plane of the ecliptic.

Solar System observations cont. 4. All of the planets except Uranus and Pluto have axes of rotation that are nearly perpendicular to the plane of the ecliptic. 5. The 4 innermost planets all have similar densities and compositions. 6. The 4 outer planets that are gas giants have similar densities and compositions.

Solar System observations cont. 7. All planets except Venus and Uranus and most of the planetary moons rotate in a counterclockwise direction. 8. There is an asteroid belt between Mars and Jupiter.

Solar Nebula Theory • ~ 4. 6 bya a cloud (nebula) of interstellar material (mostly H and He) within a spiral arm of the milky way galaxy began to contract and flatten into a rotating disk • Disk rotated and most of the mass concentrated in the center • Surrounding the central disk, the turbulent rotating nebula of interstellar gases began to cool and condense, forming solid particles

Solar Nebula Theory • Massive central disk formed a star, our sun • Sun began to emit electromagnetic radiation • Solid particles in the nebula collided and accreted (stuck together), becoming larger and more massive forming planetesimals • As more and more particles accreted, the planetesimals formed planets

Understand meteorites and the age of the earth

Meteorites • Believed to be examples of the original material from the solar nebula. • Used to learn about the origins of our sola system and the planets