2. 1. How do scientists measure our distance from stars that are too far to use the parallax effect? 2. How is this this related to absolute magnitude? Times Up!

4.  Make a T-chart ◦ On one side list 3 things you think you know about stars. ◦ On the other side 3 list things you want to know about stars.

5.  Not really empty  Stars, planets, etc.  Interstellar medium ◦ Dust and Gas ◦ Nebulas Orion Nebula http://hubblesite.org/gallery/album/nebula/pr19 95044a/ Large Magellanic Cloud http://hubblesite.org/gallery/album/nebula/pr200605 5a/

6.  Nebulae are usually composed of 70% Hydrogen, 28% Helium, 2% heavier elements  A force compresses the particles, they begin to contract together

7.  Gravity at work ◦ More mass means more gravity; more gravity results in more mass, etc.

8.  As the Gravitational forces between the particles increase, they begin to spin more rapidly  Here is a demodemo  The shrinking, spinning region begins to flatten onto a disk called a PROTOSTAR

9.  Increased pressure and temperature  Temperature continues to increase until it reaches about 10,000,000 O C when NUCLEAR FUSION begins and a star is born!

10. Little mass  lots of energy E = mc 2

11. Fermi National Lab http://www.wired.com/playbook/2012/08/olympics-physics-hammer-throw/ http://www.universetoday.com/52696/nuclear-fusion-power-closer-to-reality-say-two-separate-teams/  High temperatures  2 particles become 1  Releases a lot of energy

12.  Energy heats up gas and causes outward expansion.  Gravity pushes in.  Forces balance out = Hydrostatic Equilibrium ◦ Stable adult stage star