Clumps increase in size [accretion]pressure and temperature increases [due to KE of particles]
2. Protostarwhen forces are in equilibrium : gravity collapses particles together, high temperature/pressure pushes particles apart.At equilibrium Gas pressure = gravity
4. STAR If enough mass, critical temperature protostar core begins to fuse H into He :star is born.
The star is stable while the gravitation pulling the star together is balancedby the internal pressure pushing it apart.
During lifetime, stars fuse Hydrogen into Helium and then fuse helium into Carbon.
On the main sequence, hydrogen is fused into helium H is fused into He..
Mass-luminosity relationship for Main Sequence StarsL = Lo[M/Mo]3.5Lo = luminosity of SunMo = mass of Sun
The Herzsprung-Russell Diagram H-R diagramshows relationship of luminosity, temperature, size
Mo is the mass of the SunLow mass stars: 0.5Momedium mass stars: 0.5Mo – 3Momassive stars: >3 Mo
Larger, hotter stars burn out very fast - in a few million years.Smaller, cooler stars burn slowly for billions of years
The Sun is a medium yellow star.The surface temperature is about 6000KThe Sun has a life expectancy of about 10 billion years
Try the interactive star lab: http://aspire.cosmic-ray.org/labs/star_life/starlife_sequence.html
After becoming red giantlow mass stars [mass of Sun] shrink into white dwarfs.Radius is close to radius of Earth.
Medium mass stars [ 1.4 to 3 Mo] expand into Red Giants , collapse and then explode into a supernova
Massive stars collapse and begin to fuse carbon.They explode as supernova and the core is crushed into a black hole .
After about 100,000 years the protostar has drawn in enough dust and gas to become a star.
When core temperature reaches 10 million degrees, H begins to fuse into He, releasing energy [heat]
Black hole swallows a starhttp://www.youtube.com/watch?v=O3Z5AS3TTS4