Inner/Outer planets and formation of the Solar System

What is protostar

A contracting nebula with enough mass to form a star.

Explain the role of gravity in the formation of a star

A star is formed when a contracting cloud of gas and dust becomes so dense and hot that nuclear fusion begins. Pressure from fusion supports the star against the tremendous inward pull of gravity. This new energy source stabilizes the young star, and it joins the main sequence.

Explain the accretion disk

Accretion is the process of adding mass in the formation of the planets by colliding with other planetesimals.

What is supernova

An enormous explosion in which the byproduct's of a supergiant star's lifetime of fusion are flung into space.

Explain characteristics of the inner planets

The four planets closest to the sun - Mercury, Venus, Earth, and Mars are all often called the terrestrial planets. These planets are similar in structure to earth. The four inner planets are all relatively small and dense, and have rocky surfaces. Like Earth, they all have a crust, mantle, and iron core. All of the terrestrial planets have rocky crusts. Mercury and Mars have surfaces that are pockmarked by craters. On Earth and Venus the craters have disappeared because the service is continually being altered. The surfaces of the other terrestrial planets change much more slowly, so more craters are visible. Mercury is the smallest of the terrestrial planets, and the closest planet to the sun. Venus' thick atmosphere is composed mostly of carbon dioxide, which traps heat and raises the planet's temperature. Earth's surface has a suitable atmosphere and temperature range for water to exist as a liquid. Mars shows evidence of once having a great deal of liquid surface water. Scientists now hypothesize that asteroids are remnants of the early solar system that never came together to form a planet.

Explain the characteristics of the outer planets

The outer planets are made up of Jupiter, Saturn, Uranus, Neptune, and Pluto. Jupiter is the largest; most mass, most moons; and great red spot. Saturn is 2nd largest; known for rings; atmosphere the largest; lowest average density; 62 moons orbiting it. Uranus is very cold; atmosphere mostly hydrogen & helium; large amount of methane giving the planet a blue-green appearance; dense core; axis of Uranus's rotation is tilted more than 90 degrees. Neptune has about the same composition and is about the same size as Uranus; bluish color comes from the methane in its atmosphere; large storms in its atmosphere. Pluto is much smaller than the inner or outer planets. Diameter half of Mercury's. During a small portion of its orbit its swings closer to the sun than Neptune. Rotation axis that is tilted more than 90 degrees. Has three moons: Charon, Nix, and Hydra.

Explain the nebular theory

The solar system formed from a rotating cloud of dust and gas. The solar nebula formed from the material expelled by previous stars.