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!

 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.

 Not really empty  Stars, planets, etc.  Interstellar medium ◦ Dust and Gas ◦ Nebulas Orion Nebula a/ Large Magellanic Cloud 5a/

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

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

 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

 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!

Little mass  lots of energy E = mc 2

Fermi National Lab  High temperatures  2 particles become 1  Releases a lot of energy

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