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Stars & Galaxies

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M
Mr C Jones

The document summarizes the life cycle of stars and galaxies in the universe. It begins with the Big Bang 13 billion years ago which formed the first quarks, electrons, protons and neutrons. Over billions of years, hydrogen and helium atoms were pulled together by gravity to form the first stars and galaxies. The document then describes the typical life cycle of stars from their birth as protostars to their death as white dwarfs, neutron stars, or black holes depending on their mass.

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Stars & Galaxies
History of the universe 13 billion years ago – Big Bang A tenth of a second later – Quarks + electrons form. Minutes later – Quarks combine to form nucleons (protons & neutrons) 100,000 years later – Neutrons, protons + electrons combine to form simple neutral atoms of hydrogen + helium. Billions of year later – hydrogen + helium atoms are pulled together by gravity and form the first stars and galaxies. Universe continues to expands moving stars and galaxies further apart.
 
The Milky Way
The Milky Way
Life Cycle of a Star
Protostar Gravity causes matter in clouds of gas to clump together and form a protostar. The protostar continues to be pulled together by gravity and becomes denser. Hydrogen atoms get pulled so close they fuse together to form helium. This nuclear fusion process produces heat and star begins to emit light.
Main Stage Star is in equilibrium for billions of years as the supply of hydrogen undergoes fusion. The outwards force of the radiation exactly balances the inwards force of gravity so the star remains the same size.
Red Giant As the hydrogen starts to run out the star cools down, expands and turns red. It is now known as a red giant. At this stage helium atoms themselves begin to fuse and heavier more complicated elements are created.
White Dwarf When the supply of hydrogen runs out nuclear fusion stops. Gravity is now able to collapse the star in further since the force of the emitted radiation has disappeared. It heats up and its colour changes from red>yellow>white
Death of a Star What happens next depends on the mass of the star. ?
Low mass white dwarfs White dwarfs with a low mass cool down gradually. As they cool they stop emitting light. They become known as black dwarfs.
High mass white dwarfs Gravity continues to collapse the star. It suddenly explodes in an event know as supernova and ejects material into space. The remaining/left behind material collapses under gravity into a neutron star. The neutron star has an extremely high density similar to that of an atomic nucleus. It is composed entirely from neutrons with no space between them. (unlike normal matter that has a lot of empty space between the nucleus and orbiting electrons.
Supernova
Neutron Star
Black Holes If the neutron star has a large enough mass it will continue to collapse even further and become a black hole. The black hole has a mass occupying a single point (i.e. 0 volume) and an will therefore have an infinite density. Gravity is so strong nothing can escape its gravitational field (this includes light).
gravity large star small star nuclear fusion super- nova nebulae Life cycle of a star
 

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Stars & Galaxies

  • 2. History of the universe 13 billion years ago – Big Bang A tenth of a second later – Quarks + electrons form. Minutes later – Quarks combine to form nucleons (protons & neutrons) 100,000 years later – Neutrons, protons + electrons combine to form simple neutral atoms of hydrogen + helium. Billions of year later – hydrogen + helium atoms are pulled together by gravity and form the first stars and galaxies. Universe continues to expands moving stars and galaxies further apart.
  • 3.  
  • 6. Life Cycle of a Star
  • 7. Protostar Gravity causes matter in clouds of gas to clump together and form a protostar. The protostar continues to be pulled together by gravity and becomes denser. Hydrogen atoms get pulled so close they fuse together to form helium. This nuclear fusion process produces heat and star begins to emit light.
  • 8. Main Stage Star is in equilibrium for billions of years as the supply of hydrogen undergoes fusion. The outwards force of the radiation exactly balances the inwards force of gravity so the star remains the same size.
  • 9. Red Giant As the hydrogen starts to run out the star cools down, expands and turns red. It is now known as a red giant. At this stage helium atoms themselves begin to fuse and heavier more complicated elements are created.
  • 10. White Dwarf When the supply of hydrogen runs out nuclear fusion stops. Gravity is now able to collapse the star in further since the force of the emitted radiation has disappeared. It heats up and its colour changes from red>yellow>white
  • 11. Death of a Star What happens next depends on the mass of the star. ?
  • 12. Low mass white dwarfs White dwarfs with a low mass cool down gradually. As they cool they stop emitting light. They become known as black dwarfs.
  • 13. High mass white dwarfs Gravity continues to collapse the star. It suddenly explodes in an event know as supernova and ejects material into space. The remaining/left behind material collapses under gravity into a neutron star. The neutron star has an extremely high density similar to that of an atomic nucleus. It is composed entirely from neutrons with no space between them. (unlike normal matter that has a lot of empty space between the nucleus and orbiting electrons.
  • 16. Black Holes If the neutron star has a large enough mass it will continue to collapse even further and become a black hole. The black hole has a mass occupying a single point (i.e. 0 volume) and an will therefore have an infinite density. Gravity is so strong nothing can escape its gravitational field (this includes light).
  • 17. gravity large star small star nuclear fusion super- nova nebulae Life cycle of a star
  • 18.