REMEMBER IT!

• – It began as a hot ball of matter and radiation but as it expanded it cooled and became transparent.
• – For a few billion years the Universe was only dark, empty space, filled with helium and hydrogen.
• – The stars and galaxies were formed due to gravitational attraction.
• – Clumps of space matter appeared and as they became denser so their gravitational attraction increased.
• – A star is created from a cloud of dust and gas. Gravitational attraction joins matter together to form a protostar.
• – Stars radiate energy due to hydrogen fusion within their cores.
• – Once the hydrogen nuclei have run out the star swells outwards and becomes a red giant.
• – After all the light elements in the core have run out fusion and radiation release stops and the star collapses in on itself, forming a white dwarf.
• – Small stars, which have low mass, remain as white dwarves and then become black dwarves.
• – Larger stars, which have high mass, continue to collapse until a supernova occurs.
• – The core of the star is compressed into a neutron star.
• – If the neutron star is large enough it can then becomes a black hole.
• – Light elements were created due to fusion within stars.
• – Heavy elements are formed from supernovas.
• – Planets are formed from supernova debris being brought together by gravity so are formed from all the known elements.
• – Space probes and radio telescopes are used to look for other signs of life in space.

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TEST IT!

1. Evidence suggests that the universe began approximately 13 billion years ago after the Big Bang.

a) What is meant by the Dark Age of the Universe?

b) What two elements was the Universe composed of during the Dark Age?

c) Explain how stars and galaxies formed from uncharged atoms.

2. A star begins its life as dust and gas.

a) Connect the right description with each stage of the life of a star.

protostar radiates due to hydrogen fusion

red giant clouds of gas and dust merge

white dwarf hydrogen nuclei run out and the star swells

neutron star formed after a supernova

star smallest and densest state

b) How is a black hole formed?

c) Describe the gravitational field of a black hole.

3. Light elements were first created due to fusion taking place within stars.

a) Give an example of a light element.

b) What is the cataclysmic explosion which creates heavy elements?

c) Attempts are being made to search for extra-terrestrial life forms in space. Describe two ways in which this is being attempted.

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ANSWERS

1. a) Before the stars and galaxies formed after the Big Bang when there was just empty space and background microwave radiation was formed.
b) Helium and hydrogen
c) Uncharged atoms were attracted to each other due to gravitational force. They formed clumps of matter which, as they became denser, formed larger clumps. This resulted in the stars and planets.

2. a)

protostar ? clouds of gas and dust merge

red giant ? hydrogen nuclei run out and the star swells

white dwarf ? smallest and densest state

neutron star ? formed after a supernova

star ? radiates due to hydrogen fusion

b) From neutron stars with a large enough mass.
c) It is very strong. Electromagnetic radiation is unable to escape one.

3. a) Answers include:
Hydrogen
Helium
Carbon
b) A supernova
c) Space probes to detect chemical and microbes in the soil, rocks and atmosphere.
Radio telescopesto search for technological signals from other life forms.