GCSE WJEC physics- stars and planets

stability of stars

in main sequence forces B

when hydrogen down star will fuse helium + heavier elements to maintain fusion

star swells as grp >gf - forces UB

eventually grp<gf- star shrinks

low mass star (our sun) life cycle

protostar → main sequence → red giant → white dwarf

high mass star life cycle

protostar → main sequence → red super giant → supernova → black hole OR neutron star

further to the right of the graph

the cooler it is

higher up the graph

the bigger + brighter the star

gas + radiation pressure direction + trying to

outwards → trying to make star bigger

force of gravity direction + trying to

inwards → trying to make star smaller

stable star

force of gravity = outwards force of pressure

how elements heavier than iron made

supernova

how elements heavier than helium up to iron made

red (super) giant stars

how heliums made

main sequence stars

how hydrogens made

the big bang

black hole

if star is one of biggest in universe will becomd bh- have gravity so strong nothing can escape (not even light)

neutron star

if isnt one of biggest stars will become ns- very dense + filled with neutrons

white dwarf

when star cant fuse anything, sheds outer layers + collapses into wd- cools down and dims overtime

red giant

once hydrogen has run out star expands- can fuse heavier elements together (up to iron)

red super giant

if its much bigger than sun it will become this once run out of hydrogen

supernova

huge star explosion where all elements heavier than iron formed

main sequence

protostar not hot enough to fuse hydrogen → becomes ms (stars spend most of its life as this- fusing hydrogen into helium)

comet orbit

elyptical (rugby ball shape)

distance light travels

time x speed of light

protostar

cloud of gas + dust collapses due to gravity to form a baby star

light year (ly)

distance light travels in 1 year

astronomical unit (AU)

mean distance from the earth to sun

why we use other measurements

distances in space are so big (doesn’t make sense to use metres)

universe contents (smallest → largest)

earth → sun → solar system → milky way → universe

our solar system

milky way galaxy

ice giants

uranus + neptune

gas giants

jupiter + saturn

rocky planets

mercury

venus

earth

mars

(first 4)

comets

lumps of ice + dust that travel through solar system

solar system formed of…

dust + gas

solar system order

mercury (my)

venus (very)

earth (eager)

mars (mum)

— asteroid belt

jupiter (just)

saturn (served)

uranus (us)

neptune (nachos)