Topic 8 - Space Physics

the sun lies at the centre of our solar system it is ….

heliocentric

what galaxy is our solor system part off?

milky way

what are planets made of (small and big)

• small planets are made mainly of rock

• big planets are made mainly of gas

all planets orbit the sun …

on the same plane

all planets rotate but …

• they have different speeds

• some planets rotate in the opposite direction due to past collisions

why do larger planets have rings?

because their gravitational field is so strong it attracts debris

explain the geocentric model

• the earth was the centre and everything orbited it in perfect circles

• with a fixed background of stars

then 600 years later the heliocentric model was made because..

• mars retrograde motion → earth obits the sun faster than mars, so we undertake it so it appears in reserve in the sky

• Galileo observing moons orbiting Jupiter showed not everything orbited Earth

• Kepler showed that the planets orbited in ellipses not circles

as planets orbit the sun …

• the gravitational force causes the planet to change direction constantly

• its velocity is always changing

• the force causes the planet to accelerate without it increasing speed

for a stable orbit:

• if the planet moves closer to the sun the gravitation attraction to the sun increases (forces and acceleration increases)

• so orbital speed of planet increases

Life cycle of a star (start to star)

• the gravitational pull between dust and gas particles draw them together

• the cloud becomes more concentrated as the particles get closer

• the temperature and pressure of the cloud increases as particles get pushed together eventually they can fuse together

• fusion occurs releasing a large amount of energy

• the cloud collapses due to gravity forming a star

fusion

• occurs as the light (hydrogen) nuclei fuse together to form helium nuclei

• creating a large amount of energy

life cycle of a star (super giant)

• eventually the star runs out of gas to fuse so it collapses

  • if its a red super giant the star will increase pressure and temperature of the core meaning heavier elements can fuse

  • it then becomes unstable because it is so big,

  • it then collapses, rebounds on its centre and produces a supernova

  • then it turns into a neutron star or a black hole

life cycle of a star (normal sized)

• eventually the star runs out of gas to fuse so it collapses

  • less fusion occurs

  • the star collapses produces a nebula (lower scale supernova)

  • and a white dwarf remains

light appears red shifted from galaxies ….

moving away from earth

how do we know the universe is expanding

the change with distance of each galaxys speed

as wavelengths appear to get larger (more red) …

frequency decreases as the source is further away

what does red shift show?

• the universe is expanding

• initially it was formed from one point

Cosmic microwave background radiation

• When the universe was very young, everything, the first stars and rock, would be very hot, and should have emitted lots of short-wavelength radiation

• This radiation, as the universe expanded over time, would have been stretched to become microwaves

• Which proves that the hot young universe has cooled and expanded since

why is the big bang the most accepted model?

it accounts for all the experimental evidence