Lecture Nov. 14 Jennifer Blazejack

Introduction
12.1 : Star Birth
12.2: Life as a Low-Mass Star
12.3: Life as a High-Mass Star
Conclusion
Introduction
We looked at the big book of the cosmos. We were told to pick a topic for the paper and the slide show. If we complete them before the end of term we can present them early. We were told about the eclipse and the shower that would be happening.
Star Birth
A large cloud can create a whole cluster of stars.  Stars born in the coldest and densest parts are called molecular cloud. These clouds look like "ghosts" because they emit infrared red light from dust grains absorbed in the visible light. Prostars can become cloud fragments which rotate quickly, eventually becoming flat like a pizza. Astronomy is based on observations and that is how these "pizzas" are identified. Collusions are another name for friction, like when bumper cars collide.
Life as a Low-Mass Star
Prostars turn into main sequence stars. Main sequence stars will eventually become red giants.  An important event that takes place is called hydrogen shell fusion. It forms around the core of the star.  Helium fusion occurs when hydrogen fusion goes at a higher speed. Helium fusion forces nuclei to collide at higher speeds. This can eventually lead to a helium flash which happens when the core temperatures rise rapidly and then expands the core and then shrinks. Brown dwarfs are star like objects that are not massive enough to start fusion.
Life as a High-Mass Star
This is when a supernova can happen. Back in 1000 A.D. China, a supernova was recorded and lasted ten days, day and night.  The CNO cycle converts hydrogen into helium by using carbon, nitrogen, and oxygen as catalysts. A greater core temperature allows hydrogen nuclei to overcome greater repulsion. Helium capture builds carbon into oxygen, nitrogen, and magnesium. Iron is considered a dead end for fusion because iron doesn't release energy. Iron builds up in the core until degeneracy pressure can no longer resist gravity (the core suddenly collapses and creates the famous supernova explosion) and then the neutrons collapse to the center and create the neutron star.
Conclusion
We were briefly given an overview of section 12.4 in class. We were told that the chapter 12 quiz will be due after Thanksgiving break and that it was posted on the blog.