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Space (our solar system (gravity provides the force that creates orbits…
Space
our solar system
In our solar system there is 1 sun + 8 planets and 1 dwarf planet, these orbit the sun
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red shift
universe is expanding
evidence
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wavelengths are all longer than they should be, they're shifted towards red end on spectrum (red shift)
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more distant galaxies, have greater red shifts than nearer ones= they are moving away faster
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theories may change
observation of supernovae in 1998 onwards appear to show distant galaxies are moving away from us faster and faster (speed they are receding is increasing)
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dark matter= unknown substance which holds galaxies together but does not emit electromagnetic radiation.
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the life cycle of stars
- nebula= stars initially form from a cloud of dust and gas
- protostar= gravity pulls dust and gas together, temperature rises as star gets denser, more particles collide with each other. when temp gets high enough, hydrogen nuclei undergo nuclear fusion to form helium nuclei- produces lots of energy which keeps core hot
- main sequence star= star enters long stable period, outward pressure (caused by nuclear fusion that tries to expand star) balances force of gravity pulling everything inwards (equilibrium)
4a. red giant= eventually hydrogen runs out. star swells and surface becomes red because surface cools Fusion of helium and other elements occurs, heavier elements up to iron are created in core (happens in small star)
5a. white dwarf= sun becomes unstable and ejects the outer layer of dust and gas, leaving a hot dense solid core
6a. black dwarf= white dwarf cools down and emits less and less energy until it no longer emits a significant amount
4b. red super giant= hydrogen runs out. star swells and surface becomes red. Fusion of helium and other elements (gold, uranium)
5b. supernova= big stars start to glow brightly again as they undergo fusion and expand and contract several times. eventually they explode and eject elements across the universe to form new planets
6b. neutron star=exploding supernova throws the outer layers of dust into space leaving a very dense core.
7b. black hole= if star is big enough it becomes a super dense point in space that not even light can escape from