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SPACE (The solar system (Also contains moons, asteroids and comets (moons…
SPACE
The solar system
Sun, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
Also contains moons, asteroids and comets
moons are natural satellites that orbit planets
Stars form from clouds of dust and gas
Lifecycle of a star
In the main-sequence star, hydrogen starts to run out and the outward force is smaller than the inward force and this causes the star to collapse inwards. this also causes the stars temperature to increase.
The star expands to form a red giant and at some point this red giant stops fusing helium.
At this stage, the star shrinks and forms a white dwarf which gradually cools down as it doesn't carry out fusion.
This eventually forms a black dwarf when it stops releasing energy.
Stars that are much bigger than the sun:
1 - main sequence star expands into a red super giant
2 - helium nuclei fuse
3 - the star explodes called a supernova
4 - the temperature is high enough to make elements heavier than iron
5 - after the supernova, the remains of the star can form a neutron star OR a black hole.
Orbital motion
The earths orbit is virtually circular. the force of gravity acting between the sun and the earth holds the earth in its orbit
With circular objects, the force of gravity leads to a change in velocity but not a change in speed.
Red-shift
If we take light from the sun and put it through a prism, a spectrum is made
The dark lines in the spectrum represent how certain elements in the sun absorb light of specific wavelengths
In the spectrum for light from different galaxies, the lines have shifted towards the red end of the spectrum and this is called red-shift. this red-shift tells us that galaxies are moving away from each other and this has caused their wavelengths to increase.
Very distant galaxies have a very large red-shift. this means that they are moving away very fast. the fact that distant galaxies are moving away faster shows that the universe is constantly expanding, supporting the BIG BANG THEORY.
Clouds of dust and gas are called a nebula and a nebula is mainly full of hydrogen
1 - gravity causes the cloud of dust and gas to collapse
2 - as the dust particles move faster, the temperature rises to a million degrees
3 - this is called a protostar
4 - if the temperature gets high enough, the hydrogen nuclei join to form helium
5 - the protostar has now turned into a star
6 - in the star, a force of gravity acts inwards and the energy from nuclear fusion creates a force acting outwards, balancing each other
THIS IS NOW A MAIN - SEQUENCE STAR
