ASTROPHYSICS

define universe

large collection of billions of galaxies

define galaxy

large collection of billions of stars

why does gravitational field strength vary, 2 reasons

• depends on MASS OF BODY CREATING FIELD, larger the mass - stronger the field, weight more on earth is bigger

• depends on DISTANCE, closer to a star/planet - stronger the gravitational force is

as the gravitaional force gets stronger, what needs to balance it

instantaneous velocity

as you go closer to a star or planet, what do u need to do with speed to remain in orbit

increase speed

for an object in a stable orbit, if the speed changed… what else must change?

the size of orbit must aswell, faster moving objects smaller radius

differences in orbit between moon + planets, to comets

moons + planet → almost circular orbit

comet → very eliptical, sun one end

comet → longer orbital periods than earth, travel edges of solar system - travels fastest near sun because of increased pull of gravity

4 things gravitational force causes:

1. moons to orbit planets

2. planets to orbit sun

3. artificial satellites to orbit earth

4. comets to orbit Sun

if an object is travelling in a circle it is…

• constantly changing direction - must be force acting

this force = centripetal force, acts towards centre

• causes objects to fall towards what it is orbitting but since it is already moving, it just causes it to change direction

• the object keeps accelerating towards what its orbiting, but the instantaneous veolicity (right angle) keeps travelling in circle

gravity makes this happen

how can stars be classified by their colors:

.colour of star depends on visible light it emits → but how much being emitted depends on surface temp

hotter vs cooler star frequencies emitted

hotter star emits more light of higher frequencies

cooler star emits more light of lower frequencies

what is lumonosity

amount of energy emitted by star per second