MODULE 8 IQ 1 Flashcards
cosmological principle
universe is isotopic and homogeneous
Alexander Friedmann
used Einstein’s theory of general relativity to provide evidence for the universe to be expanding
edwin hubble discoveries
the further the galaxies were moving away from the Earth, the greater the degree of the red shift –> translational velocities are greater
- first evidence of the expanding universe
edwin hubble equation
v = H(0)d
big bang model
universe originated from a singularity
- as the universe expands, the energy density and thus temperature drops
- when temperatures are cooler, complex particles are able to be formed
timeline of big bang
big bang, inflationary epoch, quarks/leptons era, nucleons, nucleosynthesis, photon epoch, dark ages, accretion
the big bang time of big bang timeline
temperature : 10^32 K
time: <10^-43 s
- beginning of the Grand unified Theory (GUT)
- gravity separates from the fundamental forces
inflationary epoch during big bang timeline
universes expanded at a factor of 10^26 in all directions
time: <10^-32 s
- strong force separates from the electroweak force
- rapid expansion explains the cosmic microwave background radiation (CMBR, 2nd evidence for why the universe is expanding) which is almost uniform
quarks/leptons era during big bang timeline
- universe has cooled enough for matter to form
time: <10^-6 s - electromagnetic and weak force separate
4 fundamental forces
gravity
electromagnetic force
electroweak force
strong force
nucleons in the big bang timeline
- quarks combine to form protons:neutrons (7:1)
time: <10^-4 s
nucleosynthesis in big bang timeline
p + n –> nuclei
time: 225-1000 years
- 1/4 of universe mass is helium nuclei while rest if hydrogen nuclei –> initially, the universe was radiation dominant
- universe is opaque
photon epoch + recombination in big bang timeline
- photon decoupling photons (fall out of thermal equilibrium with each other) –> universe becomes transparent
- incited CMBR (microwave radiation –> long wavelength & shortest frequency)
dark ages in the big bang timeline
- no visible or infrared light as there were no stars
time: 377 000-400 million years
accretion in the big bang timeline
- increase of matter –> gravity –> organisation into large scale structures such as stars and galaxies
- protostars begin to form
- temperature cooled down by a factor that allowed particles to be affected by gravity
- increase in gravity –> clouds of hydrogen and helium –> fusion –> heat and light
what is big bang nucleosynthesis
main sequence stars fuse hydrogen into helium
what are the type of big bang nucleosynthesis
proton-proton chain, CNO cycle, triple-alpha process
what type of stars does proton-proton chain occur in
smaller, cooler stars
proton-proton chain overall equation
4^1H → ^4He + 2e^+ + 2v + 2(gamma)
what type of stars does CNO cycle occur in
bigger MS stars
- faster fusion sequence
CNO cycle overall equation
4^1H → ^4He + 2e^+ + 2v + 3(gamma)
when does triple alpha process occur
when MS star burns up into red giant
triple alpha process equations
^4He + ^4He → ^8Be + ^4He
^8Be + ^4He → ^12C + ^4He
^12C + ^4He → ^16O (most stable oxygen)
luminosity in Hertzsprung-Russell Diagram
total power radiated given by
L = 4(pi)d^2b
apparent brightness in H-R diagram
power received by a star from an observer at a point of reference per unit area
b = L/4(pi)d^2
spectral class H-R diagram
OBAFGKM
- divided from 0-9
- temperature and spectral class are related to star’s colour
magnitude in H-R diagram
more positive absolute magnitude are SMALLER
main sequence stars
- 90% of all stars
- produce energy by fusing hydrogen into helium
red giants
- above MS stars, underneath supergiants
- evolve from smaller MS stars after they have depleted their hydrogen source
supergiants
- top of HR diagram
- extremely luminous due to large SA
- lower intensity of radiation –> low surface temperatures
white dwarfs
- bottom left of HR diagram
- remnants of old stars with high surface temperature but no energy production left
- low luminosity due to small SA
brown dwarfs
- bottom right of HR diagram
- fuses hydrogen into helium slowly, lasts forever
evolutionary path of small MS star
hydrogen fusing into helium –> when all hydrogen is fused –> gravitational collapse –> higher temperature –> helium fuses to larger elements –> increased outwards radiation pressure –> red giant
evolutionary path of red giant
fusion in core with larger elements –> star shrinks –> outer layers are blown away due to electrostatic separation –> gaseous planetary nebula –> white dwarf
evolutionary path of large MS star
large MS star –> red supergiant –> huge repulsion between nuclei –> supernova –> blows away most of star mass –> neutron star or black hole
