Space physics gcse aqa,

what do all stars begin as

nebula (a cloud of dust and gas)

what are nebulae pulled together by to form

pulled together by gravity to form a protostar

what does the gravitiational attraction cause to increase and what does this cause

causes the density of a protostar to increase, causing more collisions between particles to occur, causing temp to rise enough for nuclear fusion to occur.

what fuses in main sequence stars to form heluim

hydrogen

why are main sequence stars stable

equilibrium between the force of gravity acting inwards on the star then the forces pushing outwards caused by the energy released by nuclear fusion

what happens to main sequence stars as they begin to run out of hydrogen

as there’s no more fusion occurring the star begins to collapse in on itself as energy released by fusion balances the inward pull of gravity

the core begins to contract as it does so, it releases thermal energy,a s the gravitational energy is converted into thermal energy

however even though the core has run out of hydrogen the outer layers haven’t and so they comtinue fusion, fusion begins in a shell around the core, where the remaining hydrogen fuses into helium

The energy produced by shell fusion causes the outer layers of the star to expand. As the star grows in size, it cools down and becomes a red giant.

what is the fusion in stars responsible for

producing all naturally occurring elements up to iron

what does the life cycle of a star after the main sequence depend on

mass

what happens to stars that are the same size as the sun after the main sequence

they become red giants

what happens to red giants once they eventually eject their outer layer

they become white dwarfs which cool to become black dwarfs

what happens to stars bigger than the sun

they turn into red super giants

what happens when red super giants explode in supernova

they form heavier elements than iron ejecting them into the universe

what do supernova stars leave behind

either a neutron star or for stars with a high enough mass a black hole

what has produced all naturally occurring elements and distributed them through out the universe

fusion in stars and supenovae

what is an orbit

the path on which one object moves around another

what do planets and dwarf planets orbit

stars

example of a natural satlelite

the moon

where is our solar system located

in the milky way

what shape are orbits

circular

why do objects travel in orbit

due to the force of gravity between two objects

what direction does gravity act in an orbit and what does this cause

acts towards the centre of the orbit, causing an acceleration which changes the velocity but not the speed of the orbiting object

when is the gravitational force the strongest

the closer you are to the object

what does a faster orbital speed mean

a smaller orbital radius for the object to be in a stable orbit

what is the effect known as red shift

The increase of wavelength of light from a distant Galaxy moving away from the earth

what does red shift do

all galaxies are moving away from us

what is the relationship between the speed of distant and nearer galaxies

distant galaxies are moving away faster

what does galaxies moving away from us suggest

the universe is expanding all galaxies are moving away from each other

what do the observations of red shift and cosmic microwave radiation support

the big bang theory

what does the big bang theory state

that the universe was once confined to a very small area that was very hot and dense which exploded and has been expanding ever since

What is centripetal acceleration?

at any instant the object is moving at a tangent to the circular path, the unbalanced centripetal force acting on the object causes an acceleration as it's still changing direction (velocity)

which direction does acceleration act in?

the centre of the circle

which are the most likley forces to act as a centripetal force?

gravity. tension, frcition and reaction

What did Edwin Hubble discover?

found that all far away objects such as galaxies are moving away from us and that this motion called their recession velocity is greater the further they are away from us

what happens to wavelength when frequency increases?

it decreases and vice versa

what is geostationary orbit?

This is a specific type of orbit in which the satellite:
- Remains directly above the equator
- Always orbits at the same point above the Earth's surface
- Moves from west to east (same direction as the Earth spins)
- Has an orbital time period equal to Earth's rotational period of 24 hours

what are uses of geostationary orbits?

- Communications
- GPS
- Satlelite navigation

what is circumpolar orbit?

- the satlelite orbits the earth passing the north and south poles
- orbit is not above the same position just scans the surface of the earth regularly
- orbits a few hundred kilometres above earth

what are uses of circumpolar orbit?

- weather forecasting
- land surveys
- astronomy

What feature is believed to be the thinly spread remains of energy released in the big bang?

Cosmic microwave background radiation- its existence supports the big bang

How do spectra show red shift

The dark lines in the spectra from distant galaxies show an increase in wavelength, the lines are moved or shifted towards the red end of the spectrum

The more red shifted the light from a Galaxy is the _____ the Galaxy is moving away from the earth

Faster

Why are dark lines present when analysing emission spectra from a starbec

Because light from a star doesn't contain all the wavelengths of the e-m spectrum as elements in the star absorb some of the emitted wavelengths so dark lines are present when the spectrum is analysed

Which two things balance and keep a main sequence star in equilibrium

Gravity and radiation pressure