C3 Stars - 4)Death of a star and Hertzsprung Russell diagram & Luminosity

4)Death of a star
Low Mass starts(after red giant)
-When He runs out, no further thermonuclear reactions are started, as the temperature is not sufficient.
-The red giant sheds its outer latyes of gas /--> planetary nebula/
-As there is no nuclear burning, there is no outward pressure to balance gravity - the core is compressed further.
-A very small, hot and dense star is produced /--> white dward/
-The white dwarf cools gradually, becoming dimmer, resulting in an /black dwarf./
Massive stars( >4 times the mass of sun of protostar)
-Further nuclear reactions start in the compressed core from C, N, O and Si fusion till iron, which is very stable
-Due to the high gravitational force of the red supergiants's core, the core collapses inwards./(implosion)/
-This gravitational collapse produces high amount of energy causing it to rebound causing a shock wave
-The explosion is called a /supernova./
-The remaining core becomes a neutron star or a black hole depending on the mass.
Hertzsprung Russell Diagram
diagram and spectral class table img:
Luminosity
-Luminosity(L) is defined as the total power output of radiation emitted by a star
-Since I=P/A; I=L/4pir² diagram exp img:
-Assumption;
-The power from the star radiates uniformly through the space
-No radiation is absorbed between the star and the Earth
Q) img:
Blackbody Radiation
-A black body is a perfect is a perfect absorber of all EM radiation.
-Since a good absorber of EM radiation will also be a good radiator, a blackbody is described to be able to emit radiation at all wavelengths.
-The amount of energy radiated by a body depends on its temperature and is given by stefan-Boltzmann law.
1-->Def, descrip-->3, stefan-boltzman law questions
radiation moving in and getting stuck inside img: