Topic 4 - Space Physics Flashcards
life cycle of stars
protostar -> main sequence ->
red ( super ) giant -> white dwarf
-> black dwarf
-> OR neutron star / black hole
how are protostars formed?
- formed from planetary nebula, which is cloud of dust and gas
- gravity makes the dust & gas spiral in together to form a protostar
how do we get from protostar to star?
- gravitational attraction causes increase in density
- particles within protostar collide more often
- temperature rises and becomes high enough for H nuclei to undergo fusion
- releases lot of energy, star is born
what is main sequence star?
- the energy released by nulcear fusion provides an outward pressure
- that is balanced by the force of gravity pulling inwards
- enters long stable period that lasts for millions of years
- Sun is in its’ main sequence stage
what happens after main sequence stage?
- H supply of star runs out
- fusion of helium and other elements
- heavier elements up to Fe created in core
- outward pressure caused by fusion is larger than inward pressure of gravity, no longer stable
death of stars about size of sun
- expand into red giant
- becomes unstable and ejects outer layer of dust and gas as planetary nebula
- leaves behind white dwarf
- as it cools down it emits less energy, until it no longer emits significant amount : BLACK DWARF
death of stars much larger size of sun ( p1)
- expand into red SUPER giants
- forms elements as heavy as Fe
- runs out of elements to fuse and becomes unstable
- explodes in a supernova
death of stars much larger size of sun ( p2)
- intense heat generated by supernova forms element heavier than Fe
- ejects them into universe
- leaves behind dense core, neutron star or black hole
- which is super dense and light cannot escape from it `
what is the Sun?
the only star in our Solar System
order of planets ( My Very Elegant Mother Just Served Us Nachos )
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
planets
large objects that orbit a star
dwarf planets
planet- like objects that orbit stars but are too small to fit criteria
moons
natural satellites that orbit planets
artificial satellites
satellites that humans have built that orbit planets
what galaxy is our Solar System part of?
it is part of the Milky Way Galaxy, which is a collection of billions of stars
orbit
a path on which one object moves around another
how do planets move around the sun
- planets move around the Sun in circular orbits
- it is constantly changing direction
- constantly changing velocity but keeping speed same
how do planets keep changing velocity?
- for an object to accelerate there must be a force acting on it
- this is directed towards the centre of the circle
- gravity between planet and the Sun
how do planets move in a circle around a star
- the object keeps accelerating towards what it’s orbiting due to gravity but..
- instantaneous velocity, which is at 90 to force of gravity keeps it travelling in a circle
how does radius of orbit affect speed?
- the smaller the radius, the faster the speed of the object
why is this?
- the closer you get to the object, the stronger the gravitational force
- the stronger the force, the faster the object needs to move
red-shift
- when the observed wavelength of light from a source moving away from us increases
light from distant galaxies
- we observer that the wavelength of light from distant galaxies has red-shifted
- this suggests they are moving away
- light from more distant galaxies is even more red-shifted…
what does this prove about the universe
- suggesting that they are moving away from us faster
- all galaxies are moving away from each other
- suggesting the universe is expanding
what is the Big Bang theory
- all matter in the universe occupied a very small space
- it was very dense and so very hot
- then it ‘exploded’, space started expanding and still going on
recent observation about rate of expansion
- expansion of universe is accelerating
