Cosmology Flashcards
What are the 3 Laws of Kepler?
The orbits are ellipses, equal areas are swept out in equal time intervals, T^2 is proportional to r^3
What is a satellite?
an object in orbit around another
First three stages of a star forming?
Nebula - cloud of dust and gas, Protostar - critical temp. fusion starts, Main Sequence
Last three stages of a small star?
Red Giant - core collapse, shell burning, White Dwarf - layers drift off, hot core, Black Dwarf - cools, invisible
Last three stages of a massive star?
Red Supergiant - layers of fusion until core made of iron, Supernova, Neutron star/black hole
What holds a white dwarf together?
Electron degeneracy pressure
What holds main sequence star together?
Gravity inwards, gas and radiation pressure outwards
What holds a neutron star together?
Neutron degeneracy pressure
What is the Chandrasekar Limit?
The max mass that electron degeneracy pressure can prevent the collapse of - 1.44Mo
What is the event horizon?
boundary of black hole where the escape velocity is greater than the speed of light
What is the Schwarzchild radius?
The distance from the singularity of a black hole to the event horizon
What is luminosity?
The total radiant power output of a star
Why are emission spectra better than absorption?
Some lines may be missing from the absorption spectrum because electrons may deexcite indirectly.
How do absorption spectra work?
Photons bombard electrons cooler gas, causing them to excite. The electrons deexcite, and scatter photons which do not reach the sensor, causing a black line spectrum.
Why are telescopes better than eyes?
wider aperture collects more light and is less similar to the wavelength of light = less diffraction = less image distortion
What is a black body?
a perfect emitter and absorbs all EM radiation
What is the Stefan-Boltzmann law?
total power radiated per unit surface area of a black body is directly proportional to temperature^4
How old is our universe?
Approx. 13.5 billion years
Steady State Theory
Matter is created continuously
How many light years is a parsec?
3.26
What is 1AU?
1.5x10^15m
What is a parsec?
The distance at which the radius of 1AU subtends the angle of an arcsecond.
What is recessional velocity?
The speed at which a galaxy is moving away from another
What is the cosmological principle?
universe is isotropic and homogeneous when viewed on a large scale
What does isotropic mean?
universe looks the same in all directions, no centre or edge to it
What does homogeneous mean?
matter is evenly distributed - no preferred location, density is constant
What are the universal laws?
theories and models of physics tested on Earth can be applied to the whole universe
What is the evidence supporting the Big Bang?
red shift shows galaxies are accelerating away, temperature and CMB matches expected cooling, 2.7K, spectrum matches a black body, relative abundance of light elements (H and He)
How is CMB evidence for the Big Bang?
shows that when matter and radiation were strongly coupled, universe was isotropic and homogeneous, temp at 2.7K, expected
Properties of CMB radiation?
isotropic, temp of 2.7K, black body spectrum
How was CMB radiation formed?
Early universe hot, matter and radiation in thermal equilibrium,
