1. Our Solar System
SPACE

2. Learning Goals To be able to measure distances in space
To be able to describe different models of the solar system
To be able to describe our sun

3. Space is so big, that we use different units to describe distances
SPACE IS BIG!
I mean ...
REALLY BIG!!!
Space is so big, that we use different units to describe distances

4. Distances in the Solar System
Within our solar system, distances are relatively small
Astronomers use a unit called the astronomical unit (AU)
1 AU is equal to (150 million) km, which is the average distance between Earth and the Sun

5. Distances Beyond the Solar System
Even the astronomical unit is too small to be used outside the solar system
Therefore, we use a much larger unit – the light year
One light year (1 ly) is the distance that light travels through space in one year
Light travels at km/s in space, so in one year, it travels about 9.5 trillion km

6. Our Solar System The Sun is the star at the centre of our solar system
It is surrounded by the 8 planets, several dwarf planets, comets, asteroids, and other celestial objects

7. Models of the Solar System
There was a time when humans believed Earth was the centre of the Universe
This meant the Sun and all other planets orbited Earth
This became known as the geocentric model (‘geo’ means Earth)
However, it did not explain everything
Some planets appeared to move in one direction, stop, and move in the opposite direction

8. Models of the Solar System
Geocentric Model

9. Models of the Solar System
In the 16th century, Nicolaus Copernicus presented a model with the Sun at the centre of the Universe
This model, the heliocentric model, better explained the motion of the planets
We now know that the Sun is at the centre of our solar system, and not the Universe

10. Models of the Solar System
Heliocentric Model

11. The Sun The Sun is approximately 4.6 billion years old
The Sun is 1 AU (150 million km) from Earth
At that distance, it takes light 8 minutes to travel from the Sun to Earth
In other words, if the Sun suddenly stopped emitting light, we wouldn’t know for 8 minutes

12. The Sun
The Sun is a medium sized star composed of many different layers
In the core, nuclear reactions occur that fuse hydrogen atoms into helium atoms
These reactions release immense amounts of energy, causing the core to reach temperatures of 15 million °C

13. The Sun
Energy produced in the core moves outward into the radiative zone
The energy continues outward into the convective zone, where cool matter sinks and hot matter rises
Energy continues outward to the Sun’s surface, the photosphere, where it escapes as light

14. The Sun The region above the surface is the solar atmosphere
The chromosphere is the inner atmosphere and is about °C hotter than the photosphere
The thin outer layer, called the corona, glows brilliantly and extends millions of kilometres into space

15. The Sun

16. The Sun’s Surface Features
Sunspots are dark regions of cool matter on the photosphere caused by twists in the Sun’s magnetic field
They follow an 11 year cycle, forming near the poles and moving towards the equator
Solar flares are huge explosions of gas and charged particles
They release huge amounts of energy and reach temperatures of tens of millions of °C

17. Sunspots

18. Solar Flares

19. Energy from the Sun
Every second, the Sun releases enough energy to meet our energy needs on Earth for the next years
It drives our weather and climate system
It provides the energy needed for life to exist on Earth

20. Success Criteria I CAN use measurements in space
I CAN describe the Geocentric and Heliocentric models of the solar system
I CAN describe features of our sun