Stars and the Universe

The life cycle of a star begins with a large cloud of dust and gas which collapses.

Five later stages of the life cycle of a very massive star are:

$\text{black hole}\quad \text{protostar}\quad \text{red supergiant}\quad \text{stable star}\quad \text{supernova}$

Place these stages in Table 9.1 in the order in which they occur.

Table 9.1

State the name of the inward force.

Further collapse is prevented by an outward force. The Sun will remain in the stable stage of its life cycle for a few billion years.

Describe what causes the outward force.

State what is meant by a 'light-year'.

State the time that passed between the explosion that formed SN185 and the electromagnetic radiation from the explosion reaching Earth.

A recently observed supernova is SN2014J.

The remnants of SN2014J are 12 million light-years from Earth, outside the Milky Way.

There is no redshift seen in the electromagnetic radiation from the remnants of SN185 but a large redshift is seen in the electromagnetic radiation from the remnants of SN2014J.

Explain this difference.

Most of the atoms found in the early Universe were hydrogen and helium.

The Universe now contains atoms of heavier elements.

Explain how the heavier elements are formed.

State the name of the nuclear reaction that occurs at the centre of the star and describe this nuclear reaction.

Explain how this nuclear reaction helps to keep the star stable.

State why the nuclear reaction can no longer keep the star stable.

Describe what then happens to the red supergiant.

State what is meant by 'a light-year'.

The Sun is one star in the Milky Way galaxy.

State the approximate diameter of the Milky Way galaxy.

diameter of Milky Way = ______ light-years

Complete Fig. 10.1 to show the stages that a massive star goes through after it has used up most of the hydrogen at the centre of the star.

Use words from the following list:

nebula      neutron star      protostar      red giant      supernova      white dwarf

State the stage in the life cycle of a star where heavy elements are formed.

Current scientific understanding is that the universe began 14 billion years ago in an event known as the Big Bang.

Explain one observation that supports the Big Bang Theory.

observation ______
explanation ______

Explain what is meant by nuclear fusion.

Describe the nuclear fusion reaction that takes place in the Sun.

State the energy transfers that occur as the cloud collapses.

The temperature increase starts a nuclear fusion reaction.

Explain why the temperature of the star eventually reaches a steady value.

State what is meant by 'a supernova'.

Describe how a protostar forms inside a nebula.

State the name of the galaxy that contains our Sun.

State what is meant by a light-year.

Near the end of its life, a massive star becomes a red supergiant.

Describe what happens inside the star as it becomes a red supergiant.

Describe how a red supergiant produces a black hole.

Describe how the heaviest elements are produced.

Describe the energy transfers that take place as the cloud collapses and forms the protostar.

Explain how the nuclear reaction in the protostar stops further collapse as the protostar becomes a stable star.

The cloud of dust and gas that collapses also contains atoms of the heaviest elements.

State which part of the life cycle of a star is responsible for the production of the heaviest elements.

A very high temperature is needed to force nuclei together.

Explain why.

A star forms from a large cloud of gas and dust in space.

Describe what happens as the star forms.