Physics Unit 8: Space Physics (Triple only)
GCSE Revision Notes
The Solar System
Our solar system is just one small part of a huge galaxy called the Milky Way, comprising billions of
stars. It contains a huge array of different objects:
Planets: Large objects that orbit a star. Orbiting around the Sun are eight planets together
with their moons.
Dwarf planets: Planet-like objects that orbit stars, but don’t meet all the criteria for being a
planet.
Moons: Orbit planets, moons are natural satellites.
Artificial satellites: Satellites that humans have built, they generally orbit the Earth.
Other objects, such as asteroids and comets.
The order of planets in our Solar System is: Mercury, Venus, Earth, Mars, Jupiter, Saturn,
Uranus, Neptune.
Our solar system is believed to have formed from a giant cloud of gas (mainly hydrogen) and
dust, called a nebula
Gravity pulled this cloud together into a giant ball.
The centre of this ball (the early Sun) got very dense and hot and eventually nuclear fusion
was able to begin.
The leftover gas and dust continued to orbit the Sun and eventually clumped together
forming the planets and other objects of the solar system.
The life cycle of stars:
1. Stars initially form from a cloud of dust and gas called a nebula.
2. The force of gravity pulls the dust and gas together to form a protostar. The temperature
rises as the star gets denser and more particles collide with each other. When the
temperature gets high enough, hydrogen nuclei undergo nuclear fusion to form helium
nuclei. This gives out huge amounts of energy, which keeps the core of the star hot.
3. The star enters a long stable period where the outward pressure caused by the nuclear
fusion that tries to expand the star balances the forces of gravity pulling everything inwards.
GCSE Revision Notes
The Solar System
Our solar system is just one small part of a huge galaxy called the Milky Way, comprising billions of
stars. It contains a huge array of different objects:
Planets: Large objects that orbit a star. Orbiting around the Sun are eight planets together
with their moons.
Dwarf planets: Planet-like objects that orbit stars, but don’t meet all the criteria for being a
planet.
Moons: Orbit planets, moons are natural satellites.
Artificial satellites: Satellites that humans have built, they generally orbit the Earth.
Other objects, such as asteroids and comets.
The order of planets in our Solar System is: Mercury, Venus, Earth, Mars, Jupiter, Saturn,
Uranus, Neptune.
Our solar system is believed to have formed from a giant cloud of gas (mainly hydrogen) and
dust, called a nebula
Gravity pulled this cloud together into a giant ball.
The centre of this ball (the early Sun) got very dense and hot and eventually nuclear fusion
was able to begin.
The leftover gas and dust continued to orbit the Sun and eventually clumped together
forming the planets and other objects of the solar system.
The life cycle of stars:
1. Stars initially form from a cloud of dust and gas called a nebula.
2. The force of gravity pulls the dust and gas together to form a protostar. The temperature
rises as the star gets denser and more particles collide with each other. When the
temperature gets high enough, hydrogen nuclei undergo nuclear fusion to form helium
nuclei. This gives out huge amounts of energy, which keeps the core of the star hot.
3. The star enters a long stable period where the outward pressure caused by the nuclear
fusion that tries to expand the star balances the forces of gravity pulling everything inwards.
