The Universe

The Big Bang Theory Scientists believe that our universe began with a big explosion of gas and dust in space. This explosion is called the Big Bang. All of this matter and energy in space was concentrated at one point before the Big Bang. They believe this explosion occurred about 15 billion years ago. Since that time, the universe has been expanding (getting bigger and more spread out).

animation of the formation of the universe: http://resources.schoolscience.co.uk/PPARC/bang/bang.htm

our solar system Our solar system consists of the sun, planets, dwarf planets (or plutoids), moons, an asteroid belt, comets, meteors, and other objects. The sun is the center of our solar system; the planets, over 61 moons, the asteroids, comets, meteoroids and other rocks and gas all orbit the Sun.

This is the compostion of our solar system: Sun: 99. 85% Planets: 0 This is the compostion of our solar system: Sun: 99.85% Planets: 0.135% Comets: 0.01% ? Satellites: 0.00005% Minor Planets: 0.0000002% ? Meteoroids: 0.0000001% ? Interplanetary Medium: 0.0000001% ?

animation of our solar system. http://janus.astro.umd.edu/javadir/orbits/ssv.html

galaxy Definition: A cluster of hundreds of billions of stars. Our galaxy is the Milky Way. The Milky Way is a spiral galaxy. Our solar system is on a spiral arm of the Milky Way.

The Milky Way Galaxy

Types of Galaxies: Elliptical galaxies Huge; contain stars, gas, and dust Held together by gravity Round-to-oval shape Mainly old stars are present

Types of Galaxies: Spiral galaxies Huge; contain stars, gas, and dust Held together by gravity Pinwheel shape Young and old stars are present

Types of Galaxies: Irregular galaxies No regular shape May show signs of a disk and/or a bulge; halo is present Usually rich in gas and dust Young and old stars are present

formation of our solar system http://www.metacafe.com/watch/1111454/formation_of_the_solar_system_great_animation/