Space

In our solar system there is one star, the sun, plus the eight planets and the dwarf planets that orbit around the sun. 

The solar system is part of the Milky Way galaxy

The Milky Way galaxy is a massive collection of billions of stars that are held together by gravity. 

The solar system was formed from a h6ge cloud of dust and gas called a nebula.

The sun was formed in the centre by gravity pulling the cloud of dust and gas together. 

When the Sun statred shining, the energy pushed most of the light gases to the edge of the solar system. 

Stars are made from dust and gas in space. The gravitational attraction between the particles pulls them together. This holds the star together very tightly.

The universe is made up of dust and gas.

A galaxy is a group of stars.

The gas particles in a star are pulled together by gravitational attraction between particles.

Stars try to expand because the the high temperature and pressure in the star pushes it outwards, forcing it to expand.

If the forces in a star are stable, it means that they are balanced.

Nuclear fusion happens when two small nuclei collide and fuse together to form a large nuclei.

When nuclear fusion occurs,  energy is released in the process.

The colliding nuclei need to have enough kinetic energy to fuse, otherwise they will repel each other and will not fuse.

The heat energy released by nuclear fusion in the star pushes outwards and counteracts gravity to make the star stable.

When the star becomes stable, it eners the main sequence stage.

Stars smaller than the sun:

- Expand and cool to turn into a Red Giant

- Contract and heat up to form a white dwarf

-Cool and fade into a black dwarf

Stars bigger than the sun:

-Expand and cool to turn into a Red Suoer Giant

-Explode to form a Supernova

-Suoernova produces either a neutron star or a black hole

They can be formed in a Supernova.

Elements lighter than iron are made by fusion in stars.

The rate of fusion is faster in a large star because tge rate of fusion is dependent on the temperature. As bigger stars have a higher mass, it means they have a hotter core to let fusion occur quicker.

Gravity provides the force to allow planets and both artificial and natural satellites to maintain their circular orbits.

Velocity is speed with a direction.

A moving object in a circle changes direction all the time. It accelerates (changes its velocity) towards the centre of the circle. The object changes in direction,  not speed, so the speed stays constant.

For an object to remain in a steady, circular orbit, it must be travelling at the right speed.

The closer you get to a star or a planet, the stronger the gravitational force is.

The stronger the force, the faster the orbiting object needs to travel to remain in orbit.