OCR Physics P1, P2 & P3

The Solar System

There are nine planets and one star in our solar system.
The names of the planets are Mercury, Venus, Mars, Earth, Jupiter, Saturn, Uranus, Neptune & Pluto.
A way to remember them in order is - My Very Easy Method Just Speeds Up Naming Planets.
The first four plants nearest to the sun is called the terrestrial planets. They are small and are the hot (Venus is the hottest).
Between Mars and Jupiter, there is an asteroid belt. They are large lumps of rock and are smaller than planets.
The next four planets are made of gas and are large compared to the first four. They have a colder temperature as they are further away from the sun.
Pluto is debated on if it is a planet and not, but can still be counted as one.
Comets are made of dust and ice. Their orbits are different to the planet orbits. It is an oval shape with the sun at one end of it. As the comet comes closer to the sun, the ice melts and forms the comet tail. The size of the comet is similar to asteroids.

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The Earth has an atmosphere which is made up of 78% nitrogen, 21% oxygen and 1% argon.
It orbits the Sun which takes 3651/4 days to complete.
The earth orbits on its axis, this is reason for seasons.
There are 4 main parts to the earth - The Crust, The Mantle, The Outer Core and the Inner Core.
The Crust is thin and quite rocky and uneven however from a far distance, it look quite spherical. Scientists have only been able to observe the crust properly.
The Mantle is a liquid but has properties like solid
The Core made of nickel and iron. The outer core is made of liquid nickel and the inner core is made of solid nickel. Scientists have predicted this to be the hottest part of the earth.

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Gravitational attraction pulls hydrogen nucleus' together and via nuclear fusion to form helium nuclei. This is called Stellar Nebula.
The star will then settle down. The outward pressure caused by the energetic nuclear reactions, is cancelled out by the gravitational attraction pulling it in. This is called a stable star which our sun is at the moment.
When the hydrogen is in the star has been used up, the star will collapse as the gravitational attraction will be still occurring and the star will then swell.
From this point the star can become two things, depending on the mass, a red planet or a red supergiant.
If the mass is low, the star be a red giant is cooler and then the outer layer would be thrown outwards and this will become a planetary nebula.
The core of the star will then shrink until it become a white dwarf.
If the mass is large, the star will become a red supergiant which a shorter life span than a low mass star.
It will then explode and become a supernova.
From this point the star can become a neutron star which occurs when the gravitational force have pulled all the mass together so much that they turn in to neutrons. The supernova could also turn into black hole which is very dense.

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