Physics IGCSE - Space Physics

Solar system

large collection of planets, dwarf planets, asteroids → all held together by force of gravity → orbits a central star

Solar system contains

1. a star → sun

2. 8 planets

3. Minor planets that orbit sun → e.g. dwarf planets + asteroids in the asteroids belt

4. Moons → orbit planets

8 planets in the solar system

1. Mercury

2. Venus

3. Earth

4. Mars

5. Jupiter

6. Saturn

7. Uranus

8. Neptune

My Very Educated Mother Just Served Us Noodles

The sun is the closest start to Earth

Light years

distance travelled by light in 1 year → measured in metres

Distance travelled by light formula

Distance travelled by light = speed of light x time taken

Speed of light

3.0 × 10⁸ m/s

Sun contains most of the mass of solar system → this is why planets orbit the sun

Orbital speed

The speed of orbit

UOM: meters per second (m/s)

Orbital speed equation

What force keeps an object in orbit around the sun

Gravitational attraction of the sun

Distance from sun increases = strength of sun’s gravitational field decreases + orbital speed of planets decrease

Sun

Star of medium size → made of hydrogen + helium → radiates its energy in infrared, visible + ultraviolet regions

Stars powered by nuclear reactions → release energy

In stable stars → nuclear reactions involve fusion of hydrogen in helium

How stable stars are formed

from protostars from interstellar clouds of gas + dust → due to gravitational attraction

Next stages of the life cycle of a small mass star

small mass star (about the same mass as the Sun): red giant → white dwarf + planetary nebula

Next stages of the life cycle of a large mass star

large mass star: red supergiant → supernova → neutron star

Next stages of the life cycle of a very large mass star

very large mass star: red supergiant → supernova → black hole

Nebula from a supernova form new stars with orbiting planets

Galaxies are each made up of many billion of stars

the sun is a star in the galaxy known as the milky way

Other stars that make up the milky way are much further away from Earth than the sun is from the Earth

Milky way is one of many billions of galaxy making up the universe

Diameter of Milky way is around 100 000 light years

Big Bang theory

1. Universe expanded from single point of high density + temperature

2. Universe is still expanding

3. Universe is approximately 13.8 billion years old