Our Solar System SPACE

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

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

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 150 000 000 (150 million) km, which is the average distance between Earth and the Sun

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 300 000 km/s in space, so in one year, it travels about 9.5 trillion km

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

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

Models of the Solar System Geocentric Model

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

Models of the Solar System Heliocentric Model

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

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

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

The Sun The region above the surface is the solar atmosphere The chromosphere is the inner atmosphere and is about 60 000 °C hotter than the photosphere The thin outer layer, called the corona, glows brilliantly and extends millions of kilometres into space

The Sun

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

Sunspots

Solar Flares

Energy from the Sun Every second, the Sun releases enough energy to meet our energy needs on Earth for the next 500 000 years It drives our weather and climate system It provides the energy needed for life to exist on Earth

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