Star Groups 30.3

Constellations• Groups of stars that form a pattern in

the sky• 88 recognized by astronomers to

divide the sky into sectors• Appear to shift to the west a little

each night due to revolution of earth so each season has a different set of constellations

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=mB0IjEdr31MJqM&tbnid=2qodd4zjkYDbvM:&ved=0CAUQjRw&url=http://lifeng.lamost.org/courses/astrotoday/CHAISSON/AT301/HTML/AT30103.HTM&ei=WdZaUt_UC6LE4AOvxYGoDQ&bvm=bv.53899372,d.dmg&psig=AFQjCNEmzPPKcAAcXbkhyAljb5rE0o9GDw&ust=1381771181427427

Leo and Orion

http://www.astronomy.ohio-state.edu/~pogge/Ast162/Movies/proper.html

…it’s not actually a constellation….

…it’s an asterism.

Galaxies• Large groups

of stars bound by gravitational attraction

• May be a trillion galaxies!

• Avg. 100 LY wide with 100 billion stars per galaxy

Types of Galaxies Spiral

Elliptical

Irregular

Hubble Galaxy Classification

Our Galaxy - The Milky Way• Cloudlike band across the sky

• Spiral Galaxy- we are in one of the armsThe sun takes 200 million years to revolve

around the center

Star Clusters

• Galaxies also contain groups of stars• They can be open clusters or globular

clusters

Globular Cluster - M80

Binary Stars

• Most stars in the galaxy are binary or multiple star systems

• They revolve around each other