Astrophysics Flashcards
what is a universe?
large collection of billions of galaxies
what is a galaxy?
large collection of billions of stars
where is our solar system?
in the Milky way
what is the difference between fission and fusion?
fission=starts with a large nucleus, the splits
fusion= starts with a small nuclei, then combines/joins
what is fusion?
this is when 2 small nuclei join together to make 1 large nuclei
explain fusion (inside the sun)
it is so hot (nuclei move very quickly) and under very big pressure in the sun that the nuclei collide with each other and combine.
what is the energy source for starts?
fusion
why does it need to be hot and under high pressure for fusion?
hot- because nuclei moves very quickly, lots of kinetic energy, in order to overcome electrostatic repulsive force
high pressure- so forced of the nuclei are closer together which increases the probability of collision
what properties are used to classify stars?
absolute magnitude
surface temperature
what is the apparent magnitude?
it’s a measure of the brightness of a star as WE OBSERVE IT FROM EARTH
what is the absolute magnitude?
it’s a measurement of the brightness of a star assuming that all starts are placed at the same distance
what is the order of evolution of starts of similar mass to the sun?
nebula/protostar
main sequence
red giant
white dwarf
red dwarf
describe nebula ( start similar to the sun)
-a cloud of dust and gas on the universe
-dust and gas attracts together due to gravitational forces
-no fusion= temp and pressure not high enough
-protostar is formed when there is enough mass
-fusion is not consistence
describe main sequence ( start similar to the sun)
-fusion as temp and pressure are high enough
-gravitational forces are balanced by the radiation pressure=the star is stable
-RADIATION PRESSURE= force exerted due to no fusion
describe the red giant ( start similar to the sun)
-begins to fuse elements heavier than hydrogen
-start produces more energy, radiation pressure increases and the star swells in size, gets bigger
-the surface turns red, as it is cooler, this is because the surface is further away from the core
describe white dwarf ( start similar to the sun)
-no fusion and no energy production
- gravitational forces collapse the star and or shrinks in size
-surface is much closer to the centre so it heats up and turns blue
describe red dwarf ( start similar to the sun)
-no fusion
-without energy production the star cools down and turns red, it will eventually turn black
what is the order of evolution of starts larger than the sun?
Nebula/protostar
main sequence
red supergiant
supernova
EITHER= neutron start OR black hole
describe main sequence (starts with bigger mass than the sun)
-tend to be hotter and higher pressure, so they appear white or blue
- fusion is occurring, which can create much heavier elements
-more mass the star is, the shorter it’s lifetime
describe red supergiants (starts with bigger mass than the sun)
-still fusion but for very heavy elements up to iron
-very hot as the centre is producing lots of energy so radiation pressure increases and the star swells in size becomes red and cools down as it is so far away from the core, where there energy and heat are produced
describe supernova (starts with bigger mass than the sun)
-huge explosion of radiating energy in to the universe
-occurs when fusion stops abruptly
-the radiation pressure reduces to 0 and the star collapses
describe neutron star (starts with bigger mass than the sun)
-this is all neutrons, nothing else
-low mass
-no fusion
describe black hole (starts with bigger mass than the sun)
-rip in the universe itself, nothing can escape it
- no fusion
when was the big bang?
13.7 billion years ago
what is the big bang?
model that scientist use to explain the early expansion of the universe
what evidence do we have for the big bang?
-red shift of galaxies
-CMBR
explain the red shift of galaxies
-light from the galaxies is found to be red shifted, meaning that the galaxies are moving away from us
-galaxies that are moving away have the greatest red shift, therefore are travelling the fastest (evidence of expansion)
explain the CMBR
-microwave radiation that is found in the universe in all directions
-as the universe expanded the wavelength of this radiation also expanded= explosion of the universe=to produce the radiation there must be a huge release of energy(start of the universe)
ONLY EXPLAINED BY THE BIG BANG THEORY
what is red shift?
is when an object emitting light moves away from us, the wavelength increase and appear more red
what is blue shift?
is when an object emitting light moves towards us, wavelength decreases and appears more blue
what is the doppler effect?
it’s an apparent shift of wavelength of signal when object moves towards/away from the observer
what is the equation linking change in wavelength, wavelength, velocity of a galaxy and the speed of light
change in wavelength/wavelength(reference) = recessional speed/ speed of light
what does gravitational force cause?
-moons to orbit planets
-planted to orbit the sun
-artificial satellites to orbit the Earth
-comets to orbit the sun
