AIM: Galaxies and the Universe

Do Now:

Compare the North Star (Polaris) with the Sun.

I. Nebular Theory

• A nebula is a cloud of gas and/or dust in space.

• the stars and planets form from this rotating disk of dust and gases because of gravity.

• a group of stars, dust, and gases held together by gravity.

• the galaxy we live in is called the Milky Way. It is 100,000 LY across and contains about 300 billion stars.

II. The Galaxy

Cherry Springs State Park, PA

CGI rendition of our Galaxy

III. The Expanding Universe• The Doppler Effect

- used to determine whether an object in space

are moving away from or toward Earth.

• When applied to light (EMS), the Doppler Effect shows:

Red Shift when the source is moving away from an observer. (wavelengths are stretched)

Blue Shift when the source is moving towards an observer. (wavelengths are compressed)

video

* Most objects are moving away from Earth. This means the universe is Expanding.

IV. The Big Bang Theory- states that at one time, the entire

universe was confined to a dense, hot, super-massive ball. About 13.7 billion years ago, a violent explosion occurred, hurling this material outward creating the universe.

• The red shift of galaxies supports the big bang and the expanding universe theories.