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Lessons 1 & 2 - The Solar System and Stars

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Paste specification here

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Print slides 2 & 3 (Could also print solar system handout)

Video to put on Google classroom

  • Start
    • Recall questions from previous topics
  • Main
    • Introduce solar system
    • Explain the birth of the Sun - handout
    • Exam question
    • Go through the life cycle of stars
    • Students annotate their handout
  • Plenary
    • exam question 1 Exam question 2
    • Optional Betelgeuse video if you have time

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P16, Lessons 1 and 2 - The Solar System and Stars

First task, answer in your book:

  1. Define nuclear fusion
  2. Describe what causes gas pressure
  3. Describe what happens to a gas when it is compressed
  4. Describe how gas pressure can be increased
  5. Define weight

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P16, Lessons 1 and 2 - The Solar System and Stars

  1. Define nuclear fusion - The joining of 2 light nuclei to form a heavier nucleus
  2. Describe what causes gas pressure - Gas particles hit the side of their container
  3. Describe what happens to a gas when it is compressed - Pressure increases, temperature increases, volume decreases
  4. Describe how gas pressure can be increased - Decrease volume, increase temperature, increase number of particles
  5. Define weight - The force acting on an object due to gravity. Measured in Newtons

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P16, Lessons 1 and 2 - The Solar System and Stars

Learning objectives:

  • To describe the contents of the Solar System
  • To describe the birth of the Sun
  • To explain why a star radiates light
  • To compare the life cycle of small and large stars
  • To describe the formation of the elements
  • To describe the forces acting on a main sequence star

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The Solar System

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The Solar System

Our Solar System is part of the Milky Way galaxy.

It consists of:

  • The Sun
  • Planets (& dwarf planets) & their moons
  • Comets - frozen rocks that move around the Sun in elliptical orbits
  • Meteors (shooting stars) - small bits of rocks that burn up when they enter the Earth’s atmosphere
  • Asteroids - rocky objects, bigger than meteors, smaller than planets, that orbit the Sun in circular orbits

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Formation of the Solar System

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Do we have any evidence that this happened?

Yes we do!

The heaviest naturally occurring element is uranium (atomic number 92). The heaviest element which can be formed inside a star through the process of fusion is iron (atomic number 26). Heavier elements are formed when stars explode, a supernova.

The presence of uranium on Earth is evidence that our solar system formed from the remnants of a supernova.

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The creation of the Sun

The Sun formed billions of years ago from clouds of dust and gas (nebula) pulled together by gravitational attraction.

The clouds merge together and become more and more concentrated to form a protostar (a star-to-be)

Fact: The Sun is about 5000 million years old and will probably continue to shine for another 5000 million years.

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Put these statements in the correct order to describe the birth of the Sun

  1. As it becomes denser, the particles speed up and collide more - temperature increases.
  2. The particles in the clouds are pulled together by their own gravitational attraction, so the particles speed up.
  3. This fusion releases energy, so it gets hotter and brighter and starts to shine.
  4. Once hot enough, the nuclei of hydrogen atoms fuse together, forming helium nuclei.
  5. A star is born!
  6. The clouds merge together and become more and more concentrated to form a protostar (a star-to-be).

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The birth of the Sun - Check your answers

2. The particles in the clouds are pulled together by their own gravitational attraction, so the particles speed up.

6. The clouds merge together and become more and more concentrated to form a protostar (a star-to-be).

1. As it becomes denser, the particles speed up and collide more - temperature increases.

4. Once hot enough, the nuclei of hydrogen atoms fuse together, forming helium nuclei.

3. This fusion releases energy, so it gets hotter and brighter and starts to shine.

5. A star is born!

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The Sun

Our Sun is a main sequence star because it is in the main stage of the life cycle of a star.

It can maintain its energy output for millions of years, until there are no more hydrogen nuclei to fuse together.

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Why do stars shine?

The energy released from fusion in the core of a star keeps the core hot and fusion continues.

The star emits gamma radiation in all directions.

The star is stable because the forces within it are balanced (equilibrium):

  • Gravity acts inwards trying to make the star contract
  • The outward force of the radiation from nuclear fusion tries to make the star expand

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Complete the exam question in your book

4 marks

Exam technique: This is a 4 mark question so you must make 4 separate points to gain full marks.

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Check

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The Life Cycle of Stars

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The Life Cycle of Stars

When a star runs out of hydrogen nuclei to fuse together, it reaches the end of its main sequence stage.

Its core collapses and its outer layers swell out.

The life cycle events are determined by the size of the star.

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The Life Cycle of Stars

Annotate your diagram with the information on the next slide

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Stars of similar size or smaller than the Sun

  1. Star swells, cools down, turns red - Red giant.
  2. At this stage, helium and other light elements in the core fuse to form slightly heavier elements.
  3. When there are no more light elements, fusion stops, and no more radiation is released.
  4. Because of its own gravity, the star collapses in on itself.
  5. It heats up and turns from red to yellow to white - White dwarf (hotter, denser, smaller).
  6. It then fades out, goes cold - Black dwarf.

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Annotate your diagram with the new information

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Stars bigger than the Sun

  • Star swells, cools down, turns red - Red supergiant.
  • It collapses and the matter surrounding the stars core compresses the core.
  • The compression suddenly reverses in an explosion called a supernova. (Outshines a galaxy for weeks)
  • Heavy elements (heavier than iron) are formed and are scattered throughout the universe.
  • Depending on its size:
    1. Smaller supernovas:The explosion compresses the core into a neutron star - extremely dense, made of only neutrons.
    2. Huge supernovas: It becomes a black hole. The gravitational field is so strong that nothing can escape (not even light).

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To summarise

Giant cloud of dust and gas that gets pulled together by gravity.

The mass of this protostar determines its ultimate fate.

Main sequence star - fusing hydrogen to make helium

Star starts to fuse elements up to iron depending on initial mass

Massive release of energy

Lighter elements drift off into space

Hot remnant of the heaviest elements - eventually it cools, stops emitting EM radiation and becomes a black dwarf

Very dense remains of the largest stars.

These have huge gravitational fields and can cause other stars to orbit them

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Formed by nuclear fusion in main sequence stars

Formed by nuclear fusion in red supergiants

Formed by nuclear fusion during supernova explosions

You are (mostly) made of atoms formed in stars!

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Crab nebula

- exploded in 11th century

Betelgeuse is a star in the constellation Orion. It is a red supergiant about 700 million times the volume of our Sun.

Betelgeuse will go supernova at some point in the future.

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What will happen when Betelgeuse goes supernova?

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Check your notes:

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Logos / symbols

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