1 of 38© boardworks ltd 2006. 2 of 38 © boardworks ltd 20063 of 38 the solar system is about 4.6...

1 of 38 © Boardworks Ltd 2006


The Solar System is about 4.6 billion years old. It was formed from a nebula – an enormous cloud of dust and gas created when a dying star exploded.

Over millions of years, the temperature rose and the globule became more compressed, causing it to start spinning.

How was the Solar System formed?

When shockwaves from other dying stars hit the nebula, it collapsed and formed a globule.

The force of the spinning shaped the globule into a central core surrounded by a disk of gas and dust. Eventually, the core became the Sun and the material in the disk formedthe planets and asteroids of the Solar System.


Which of these objects are light sources?

The Solar System is made up of various celestial objects: the Sun the planets moons asteroids comets.

The Sun is a star and a light source. It is a massive ball of hot glowing gas, which gives out huge amounts of heat and light energy.

What makes up the Solar System?


The Sun is the star at the centre of the Solar System, about 93 million miles from Earth.

Scientists used to think that chemical reactions powered the Sun, but this could not explain how it had managed to stay ‘burning’ for millions of years.

What is the Sun?

The Sun mostly consists of hydrogen and helium.

Its mass accounts for more than 99% of the total mass of the Solar System.

It is now known that nuclear fusion is the process that releases the Sun’s energy.


The planets travel around the Sun in near-circular orbits. Comets are celestial objects that also travel around the Sun, but in very elliptical orbits.

The head of a comet is a lump of ice and dust, a few kilometres in diameter.

What are comets?

The tail consists of gas and dust that are released from the comet by the heat of the Sun.

For most of its orbit, a comet is a long way from the Sun. The tail of the comet only appears when the its orbit passes nearest the Sun.


The Solar System – true or false?


A star is ‘powered’ by nuclear fusion reactions taking place in its core.

In the Sun and most stars, hydrogen atoms fuse together to form helium. This provides the energy for life on Earth.

What powers a star?

It would take 20billion nuclear power plants a whole year to produce the same amount of energy on Earth.

This process releases huge amounts of energy. Each second, the Sun produces400,000,000,000,000,000,000,000,000 watts of energy!

Nuclear fusion involves light atomic nuclei joining together (fusing) to form heavier ones.


Using nuclear fusion


However, not all elements are made in the early stages of a star’s life. Some of the heavier elements are only made when a star explodes at the end of its life.

Nuclear fusion in stars produces new atoms.

How are elements made?

When all the hydrogen has been used up, other elements are fused together to make the heavier elements of the periodic table.

In the early stages of a star’s life, light elements such as helium are mainly formed.


How do stars begin and end?


A white dwarf is formed at the end of the life cycle of a star that is about the same size as the Sun.

What is a white dwarf?

This photograph was taken with the Hubble Space Telescope and shows ancient white dwarf stars in the Milky Way galaxy.

The white dwarf stars are shown ringed in blue.


What is a supernova?


After a really massive red giant collapses in a supernova explosion, it leaves an object so dense that nothing, not even light, can escape its gravitational pull.

Some scientists believe that there are black holes at the centre of galaxies.

If light cannot escape from a black hole, then how can a black hole be observed?

How are black holes formed?

The end of the life cycle of really massive stars is different to that of massive stars.

This is called a black hole.


How can a black hole be ‘seen’?


Lifecycle of small stars


Lifecycle of large stars


1. What two elements make up most of the Sun?hydrogen and helium

Questions about stars

the Sun red giant white dwarf5. What is the fate of a star similar to the Sun?

A huge cloud of gas and dust from which a star is born.

2. What is a nebula?

nuclear fusion

3. What process has allowed the Sun to emit light and heat energy over thousands of million of years?

neutron star4. Which is the most dense, a white dwarf or a neutron star?


Terms about the lifecycle of stars


To find the Sun, you would have to shrink down to stand on the piece of dust.

When thinking about the Universe, it can be difficult to understand the size and scale that is involved.

How big is the Universe?

One way to think about this is to imagine the known Universe scaled down to the size of planet Earth.

Our galaxy would be equivalent to the size of just one micron – that’s roughly the same size as a small piece of dust!

It would then be like finding one particular grain of sand in a seven-metre-wide circular pool filled with sand!

And this is just the known Universe…


Journey through the Universe


Size in the Universe


Terms about the Universe


Identify the celestial objects


Is the Universe expanding?


Scientists examining the light emitted by stars observe dark lines in the spectrum.

What is red shift?

This red shift suggests that distant galaxies are moving away from Earth and supports the idea of an expanding Universe.

Edwin Hubble observed that the pattern of dark lines in light from distant galaxies is shifted towards the red end of the spectrum.

These dark lines are caused by different elements, such helium, in the stars being studied.

Red shift occurs because of the Doppler effect, which can be observed in sound waves and electromagnetic waves.


What is the Doppler effect?


The Doppler effect means that sound moving away from an observer appears to be lower in frequency.

It has also been observed that the further away a galaxy is, the greater the amount of red shift.

How does the Doppler effect work in space?

This means the distant galaxies must be moving away from the Earth.

The same thing happens with light from distant galaxies, which appears to be shifted towards the low frequency, red end of the spectrum.

This means that very distant galaxies must be moving fasterthan near, all of which is evidence for the Big Bang theory.


What is the Big Bang theory?

The observation of red shift is a key piece of evidence for the Big Bang theory about the origin of the Universe.

The other key piece of evidence for the Big Bang theory is cosmic microwave background radiation (CMB).

This states that the Universe ‘began’ with a colossal explosion 13,700 million years ago and has been expanding ever since.

CMB is radiation remaining from the Big Bang explosion and fills the whole of the Universe.

This radiation has cooled as the Universe has expanded andis now slightly less than 3 degrees above absolute zero.


The Universe from beginning to end


black hole – An object whose gravitational pull is so strong that nothing can escape, not even light. It is formed after a really massive star collapses in a supernova.

comet – A lump of rock and ice, which has a very elliptical orbit around the Sun.

Doppler effect – The shift in frequency of a sound wave or an electromagnetic wave due to the relative movement of the source or observer.

galaxy – A vast collection of millions of stars.

nebula – A massive cloud of gas and dust in which a staris formed.

neutron star – The very dense core that remains after a massive red giant collapses in a supernova.

Glossary (1/2)


nuclear fusion – The process in which lighter atomic nuclei join together to make heavier atomic nuclei and a massive amount of energy is released.

red giant – The huge red star formed when a star expands and shines less brightly as it starts to die.

red shift – A shift in the wavelength of light towards the red end of the spectrum. It occurs when the light source is moving away from the observer and is evidence for an expanding Universe.

supernova – The huge explosion that occurs when a massive red giant is at the end of its life.

white dwarf – The core that remains after the outer layers of a small red giant drift away.

Glossary (2/2)


Anagrams


Multiple-choice quiz

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