Formation of Planetary Systems

Formation of Planetary Systems 

Notes from October 3rd, 2012 

Brief Tour of Solar System 

The solar system exhibits clear patterns of composition and motion. These patterns are far more important and interesting than numbers, and names. The planets are either small and rocky, known as terrestrial planets, or large and hydrogen rich, known as jovian planets. 

The Sun 

The sun makes up 99.8% of our solar system. The composition of the Sun is mostly hydrogen with a little helium. The Sun is the largest and brightest object in our solar system. The Sun is a nuclear fusion power plant and converts 4 million tons of mass into energy per second. 

Mercury 

The planet Mercury has a large iron core, with average surface temperatures of 700k during the day and 100k at night. Mercury is desolate with no with or air. 

Venus 

Venus is nearly identical in size to the Earth, and rotates on its axis in the opposite direction of Earth. The greenhouse effect causes Venus to have extreme temperatures. The surface of Mercury is hidden by clouds. 

Earth

Earth is the only known oasis of life, as well as the only surface with liquid water in the solar system. The Earth's moon is unique in that it is very large compared to the Earth's size. 

Mars 

Mars is half the Earth's size, and is the last of the four inner planets. This planet used to have water flowing on it, but no longer does. The temperature of Mars is often below freezing. This is the most studied planet. 

Jupiter 

This planet has up to 63 moons, and also has many different rings. The mass is more than 300x that of Earth. Jupiter is most famous for its Great Red Spot, which is in actuality a large storm. Jupiter has 4 very large moons (Io, Europa, Ganymede, and Callisto). The moons are often referred to as Galilean moons as that is who discovered them. 

Saturn

Saturn is the second largest planet in our solar system. Saturn's rings, which are made of countless ice and rock particles, can easily be seen. In 2004, the Cassini spacecraft landed on Saturn. 

Uranus 

The composition of Uranus is hydrogen, helium, and other hydrogen compounds. 

Neptune

The axis of Neptune tilts, and this planet has many moons, including Triton. 

Pluto (and other dwarf planets)

Pluto's size is much smaller than other planets. Pluto's moon, Charon, is similiar in size to Pluto. 

Formation of our Solar System 

The solar system involves a similar orbit pattern for all of the large bodies, including planets and the Sun. There are two major types of planets, either terrestrial or jovian. Asteroids and comets also fall into these orbital patterns around the Sun and planets. However, only Earth has a large moon among the inner planets. According to the nebular theory, our solar system formed from a giant cloud of dust. The gravitational collapse of a great cloud of dust explains all the general features of our solar system. Clouds form because of the conservation of angular momentum, where particles get closer and spin in a certain direction to eventually form a cloud.