Astronomy Mr. Coyle Earth Space Science Harwood Union H.S. S. Duxbury, VT USA Planet Earth

Organization of the Universe

The Big Bang Theory The universe formed in an enormous explosion about 13.7 billion years ago All matter or “stuff” in the universe was condensed into a tiny volume

Evidence of the Big Bang Red Shift- when objects travel away from an observer their light “shifts” to the red end of the spectrum Cosmic Background Radiation- energy that is leftover from the Big Bang and is evenly distributed throughout the universe

KABOOM!! Gas and dust spread throughout space Matter separated into galaxies, which contain hundreds of billions of stars

Spiral Galaxy

The Nebular Theory About 5 billion years ago, a nebula, or a giant cloud of gas and dust collapsed This occurred within the Milky Way, which is our galaxy Where there was once only cold, dark gas and dust a Solar System was about to form..

How did it happen? Slowly the nebula shrank to form a spinning disk Gravity pulled some of the gas into the center of the disk The gas became hot and dense Nuclear fusion began and the Sun was born

What is nuclear fusion? Fusion means to “come to or to fuse together” In Nuclear Fusion hydrogen (H) atoms join together to form helium (He) This releases a LARGE amount of heat energy

Meanwhile… Gas and dust formed planetesimals or small bodies of matter Collisions occurred, gravity pulled these small pieces of matter together and protoplanets, or tiny planets were formed

Gravity Gravity is a force of attraction between two objects The larger the object, the stronger the force of gravity Protoplanets, were like magnets pulling in planetesimals from the nebula Eventually they formed planets and moons

The Inner Planets Mercury, Venus, Earth and Mars are closest to the sun They contain high amounts of Iron (Fe) Iron is heavy and didn’t travel as far as some other elements It makes up the core of these planets which are called terrestrial, because they are solid

The Outer Planets The Outer Planets, or Gas Giants, formed where it was cold, far away from the sun Very little of the heavy elements traveled this far Gas Giants are made of helium, hydrogen, and other frozen gases Some are thought to have solid cores They became HUGE

Still to come… How do stars form? What different kinds of stars exist? What happens when stars die? What is a black hole? What else is “out there” in the universe?