Galaxies

So, what is a Galaxy? A group of billions of stars, empty space, gas & dust, all held together by gravity! http://aspire.cosmic-ray.org/labs/star_life/starlife_main.html Great web site of life cycle and hr diagram

This is a galaxy. This is a galaxy. This is a galaxy. http://aspire.cosmic-ray.org/labs/star_life/starlife_main.html Great web site of life cycle and hr diagram  This is a galaxy. This is also a galaxy

Did you notice that all galaxies don’t look alike? Click on picture for link!

elliptical shaped, no arms Elliptical Galaxies elliptical shaped, no arms old stars very little gas & dust

Spiral galaxies (Milky Way) disk shaped, lots of stars in center, arms wound around. Middle age stars, lots of gas & dust

MORE Spiral galaxies …..

Barred spiral galaxies http://home.earthlink.net/~umuri/_/Graphics/Extras/HR_diagram.jpg disk shaped, arms wound around young stars –lots of gas & dust

Irregular galaxies Lacks symmetry, not a lot of stars, mostly gas & dust http://home.earthlink.net/~umuri/_/Graphics/Extras/HR_diagram.jpg Could have formed from: the collision of two galaxies or 2) stars unable to organize

Collisions of galaxies… Irregular galaxies http://home.earthlink.net/~umuri/_/Graphics/Extras/HR_diagram.jpg

The Milky Way Galaxy- Spiral Galaxy http://home.earthlink.net/~umuri/_/Graphics/Extras/HR_diagram.jpg

Some Milky Way Facts.. Contains 100-400 billion stars part of the local group- 28 closest galaxies within 3 million light years the closest galaxy to us is 150,000 light years away

The Milky Way Galaxy http://home.earthlink.net/~umuri/_/Graphics/Extras/HR_diagram.jpg The arms of the galaxy orbit the nucleus once every 200 million years.

The Milky Way Galaxy Our sun is 2/3 of the way out in one of the spiral arms. http://home.earthlink.net/~umuri/_/Graphics/Extras/HR_diagram.jpg

100,000 light-years across 10,000 light-years thick (center) 3,000 light-years on the edge