space physics Flashcards
what is the solar system
the sun and the things that orbit it (planets, dwarf planets, moon/natural satellites, artificial satellites)
what is the milky way
a galaxy (massive group of hundreds of billions of stars) containing our solar system
how do stars form
- form from a nebula - a cloud of gas, mainly hydrogen, and dust
- gravity causes nebula to collapse to form protostar
- dust particles move faster, temp rises until H nuclei undergo nuclear fusion to form He nuclei
- protostar is now a star
- fusion releases huge amount of energy. this energy balances the force of gravity acting inward
- it is now a main sequence star, lasting typically several billion years
for main sequence stars, what happens to stars the same size as our sun?
main sequence - red giant - white dwarf - black dwarf
- hydrogen start to run out, less fusion
- so gravity inward force becomes greater than fusion outward force
- star collapses inward, causing its temp to increase
- He nuclei start to fuse to create heavier elements
- star expands to form red giant
- red giant eventually stops fusing helium, shrinks to hot, dense, solid core - a white dwarf
- no fusion in dwarf so it cools down, releasing less energy, until it releases no more - a black dwarf.
for main sequence stars, what happens to stars bigger than our sun?
same as stars smaller than our sun - except when hydrogen runs out, it expands into red super giant
- when He nuclei fusion eventually stops, star explodes in a supernova
- explosion distributes fused elements throughout universe
- after supernova, remains of star either form neutron star (dense core) or a black hole (extremely dense - not even light can escape)
how are elements greater than iron produced?
- when star is red super giant, helium nuclei fuse to form elements as heavy as iron
- when fusion stops and star explodes in supernova, temperature increases
- temp is now high enough to produce elements heavier than iron
how do planets move around the sun in terms of orbit and speed
- virtually circular orbits, held by gravity between planet and sun
- circular means constantly changing velocity but constant speed
what does it mean if the speed of orbit changes
the radius must change
speed increases, radius decreases,
because higher speed requires greater force of gravity, to keep it in stable orbit
how do we know the universe is expanding
distant galaxies have increased wavelength
(pass light through prism, wavelength shifts towards red end of spectrum
what is red shift and what does it look like for galaxies of different distances
idea that wavelengths from distant galaxies shift towards red end of spectrum
near galaxies: small - moving away
distant: larger - moving away faster
what is big bang theory
initially all matter was in a very hot, dense region, which “exploded” into our universe
why might out universe by expanding faster instead of slower
universe contains matter and energy that we cannot detect - dark matter and dark energy
