Paper 1 - Astrophysics

Question 1

what is the universe

Answer 1

a large collection of billions of galaxies

Question 2

what is a galaxy

Answer 2

a large collection of billions of stars

Question 3

orbit of comet

Answer 3

around the sun

very elliptical

Question 4

orbit of moons and planets

Answer 4

slightly elliptical but pretty much circular

Question 5

orbital radius, orbital speed and time period equation

Answer 5

orbital speed = 2 x pi x orbital radius / time period

Question 6

relationship between orbital radius and speed

Answer 6

big radius = big speed

Question 7

colour gradient for temperature of stars

Answer 7

hottest -> coolest order:
blue
white
yellow
orange
red

Question 8

why are hotter stars blue but cooler stars red

Answer 8

hotter = emits higher frequency of light - short wavelength

colder = emits lower frequency of light - longer wavelength

Question 9

life cycle of a star smaller than the sun

Answer 9

nebula 
protostar
main sequence star
red giant
white dwarf

Question 10

life cycle of star bigger than sun

Answer 10

nebula
protostar
main sequence star
red supergiant
supernova
neutron star/black hole

Question 11

describe the formation of a star

Answer 11

a cloud of dust and gas called a nebula forms
gravity pulls stuff together to form protostar
temperature rises as star gets denser and more particles collide
when temperature gets high enough, hydrogen nuclei undergo nuclear fusion to form helium nuclei, giving out huge amounts of energy
reaches stable period where thermal expansion balances force of gravity pulling it in
eventually hydrogen in core begins to run out, so thermal expansion becomes less than gravity force so the star compresses
keeps getting compressed until dense and hot enough so outer layers expand to form red giant or supergiant
red because surface cools