Space physics

Star undergoing nuclear fusion

Gravity pushes towards the core and energy from nuclear fusion pushes outwards. It is at equilibrium.

Life cycle of star same size as sun

Main sequence star. Hydrogen nuclei form into helium atoms. There is less nuclear fusion outwards force and more gravitational inwards force. The star collapses inwards and the temperature increases. The leftover helium fuse together to create heavier elements and the star expands to form a red giant. It eventually stops creating helium and shrinks into a white dwarf. Nuclear fusion stops so it looses energy and it becomes a black dwarf.

Life cycle of star bigger size than sun

Main sequence star. Hydrogen nuclei form into helium atoms. There is less nuclear fusion outwards force and more gravitational inwards force. The star collapses inwards and the temperature increases. The leftover helium fuse together to create heavier elements and the star expands to form a super red giant. Helium forms heavier elements. Super red giant explodes (supernova) and it distributes elements into the universe. From this it can create a neutron star (densely packed neutrons) or a black hole (gravity so large light can’t escape)

Circular orbits

Gravity holds the earth in orbit to the sun. The gravity holds the moon in orbit to the earth

Artificial satellites

Geostationary satellites orbit once every 24 hours. They always face the earth

Gravity, velocity and speed of orbital motion

The force of gravity leads to a change in velocity (speed of object in given direction) but not a change in speed. The velocity is constantly changing but the speed is constant.

Speed and radius of orbits

If the speed of satellite/planet/moons orbit increases, the radius of its orbit decreases. Because it’s orbiting at a higher speed, higher gravity is needed to prevent it flying into space and to stay in a stable orbit.

Red shift

Increase in wavelength of light from most distant galaxies. The further away the galaxies, the faster they are moving and the bigger the observed increase in wavelength.

Redshift and galaxies

Nearby galaxies - small redshift - moving away slowly

Distant galaxies- large redshift- moving away faster

Proves the universe is expanding

Dark matter and dark energy

Possible explanation of why the universe expansion is speeding up. Matter and energy that we cannot detect.