Astrophysics Flashcards
Life Cycle of a Star
Protostar, Main Sequence, Red Giant, white dwarf, Black Dwarf
or if star has 1000 times the radius of our Sun:
Protostar, Main Sequence, Red Supergiant, Supernova, Neutron Star/Black hole
Comet; orbit, most gpe and ke, Tail
Elliptical orbit, most gpe furthest away from Star, most ke closest to sun, tail faces away from sun at all times
Main sequence star; what is it?
A star that releases energy from fusion of hydrogen to form helium.
Protostar formation
Gravity begins to pull the gases together into a ball
Red giant
fuses helium into heavier elements
White dwarf
Fusion stops, end of life, collapses, 50,000K or more
Black dwarf
white dwarf cools down, dark cold star.
Red supergiant
1000 radius of sun, heavier elements fused- eg iron. Millions of years later runs out of fuel, cools down, collapse. heat inside supernova
Supernova
Supergiant collapses, nuclear reaction, star explodes, new stars can form.
Neutron Star
RSG: Gravitational forces; centre collapses; condensed matter; neutron star - only neutrons
Black Hole
RSG: collapses; star disappears into a microscopic point - black hole
Apparent Magnitude
How bright a star is from earth.
Absolute Magnitude
How bright a star is from 10 parsecs away
Evolution of universe theory
The Big Bang theory
Big Bang Theory (probs don’t have to know - don’t memorise just brief idea)
0.1 second; 10^12K. No protons or neutrons. Highly energetic particles and photons.
Few seconds; Cooled- neutrons, protons and electrons exist
3 minutes; 10^9K
30 minutes; 10^8K nuclear fusion - deuterium and helium
700000 years; 4000K ; nuclei attract electrons - orbit, hydrogen and helium gas
Next billion years; gravity forms stars and galaxies
Now; expanding and evolving
Evidence for Big Bang
CMB, Red shift
Cosmic Microwave background radiation
remains of energy created by the Big Bang, The short wavelengths of the gamma radiation emitted in the initial explosion are believed to have become stretched due to the expansion of space into longer wavelength microwaves.
Red shift
everything is expanding- getting redder. means it all must have been in the same place at one time
Edwin Hubble looked at the light of galaxies further away from Earth and realised that the dark absorption lines showed greater red shifts. He concluded that distant galaxies had bigger red shifts because they were moving away faster.
Velocity of a galaxy formula
change in wavelength / reference wavelength
=
velocity of galaxy / speed of light
orbital speed equation
orbital speed = (2 x pi x orbital radius) / time period
