Life cycle of stars

1. Life cycle of stars

2. • During the collapse, the material heats up by frictional processes and begins to radiate infra-red radiation so astronomers are hoping to detect this to confirm the formation process. This is very difficult because the protostar would have a lot of gas and dust still surrounding it (a Bok Globule). • Stars are formed in groups as the different parts of the original nebula collapse.

3. Travelling at the speed of light (or radio wave) 300,000 km /sec 8 minutes sun pluto 6 hours 4 years nearest star

4. Andromeda galaxy Milky way galaxy 100,000 light years 100 billion stars Our sun is one of millions of stars in a group of stars called a galaxy

5. Andromeda galaxy Milky way galaxy 100,000 light years 100 billion stars Light from our nearest galaxy has taken 2 million years to reach us! Our sun is one of millions of stars in a group of stars called a galaxy

6. BIRTH OF A STAR Our sun 4,500 million years ago. * A star forms from a huge cloud of dust and gas. * Gravity slowly pulls the material together. * Rocks crash into each other and heat up. • During the collapse, the material heats up by frictional processes and begins to radiate infra-red radiation so astronomers are hoping to detect this to confirm the formation process.

7. BIRTH OF A STAR Our sun 4,500 million years ago. * A star forms from a huge cloud of dust and gas. * Gravity slowly pulls the material together. * Rocks crash into each other and heat up. * Nuclear reactions begin and the star starts to shine.

8. BIRTH OF A STAR Our sun 4,500 million years ago. * Nuclear reactions begin and the star starts to shine. Planets are natural satellites of the sun * Smaller masses cool to form planets which orbit the sun under gravity. * During a star’s life time, nuclei of lighter elements (mainly hydrogen and helium ) fuse to produce nuclei of heavier elements

9. THE HERTZSPRUNG - RUSSELL DIAGRAM L I G H T I N T E N S I T Y Newly formed stars join the ‘main sequence’ at a point on the graph that relates to its mass. Wave length of light emitted BlueRed HOTCold

10. THE STABLE LIFE OF A STAR

11. THE STABLE LIFE OF A STAR

12. THE STABLE LIFE OF A STAR - Our sun stays on main sequence for 10 billion years - If star mass is 15 x suns mass then 10 million years. Stars of greater mass than our sun (have higher core temperatures) can fuse heavier elements up to iron releasing even more energy.

19. Dark matter (ash)

21. Super nova

22. Explosion fusing heaviest known elements eg 92U

23. Explosion fusing heaviest known elements eg 92U also New young stars and condensing planets may form

26. Neutron star: p + e n v. dense !

27. Neutron star: p + e n v. dense !

28. For very massive stars, the material is so dense, the force of gravity so strong , that light itself cannot escape.

30. P3 4.2 The life history of a star similar in size to our sun Nebular Gravity draws atoms together, releasing energy Protostar Gravity draws atoms together, releasing energy star heats up but does not shine, Main Sequence star White dwarf Protostar Red giant Nebular Star The star shines during fusion of hydrogen to helium for billions of years; outward radiation pressure is balanced by inward pull of gravity. Red giant Most of Hydrogen has been used, now helium fuses to make carbon, unused hydrogen is ejected to the surface, cools and appears red. Whitedwarf Fusion stops, gravitational collapse occurs, star heats up and changes colour from red to yellow to white. It finally becomes cold dark matter.

31. P3 4.2 The life history of a star similar in size to our sun Nebular Gravity draws atoms together, releasing energy Protostar Gravity draws atoms together, releasing energy star heats up but does not shine, Main Sequence star White dwarf Protostar Red giant Nebular Star The star shines during fusion of hydrogen to helium for billions of years; outward radiation pressure is balanced by inward pull of gravity. Red giant Most of Hydrogen has been used, now helium fuses to make carbon, unused hydrogen is ejected to the surface, cools and appears red. Whitedwarf Fusion stops, gravitational collapse occurs, star heats up and changes colour from red to yellow to white. It finally becomes cold dark matter.

32. P3 4.2 The life history of a star similar in size to our sun Nebular Gravity draws atoms together, releasing energy Protostar Gravity draws atoms together, releasing energy star heats up but does not shine, Main Sequence star White dwarf Protostar Red giant Nebular Star The star shines during fusion of hydrogen to helium for billions of years; outward radiation pressure is balanced by inward pull of gravity. Red giant Most of Hydrogen has been used, now helium fuses to make carbon, unused hydrogen is ejected to the surface, cools and appears red. Whitedwarf Fusion stops, gravitational collapse occurs, star heats up and changes colour from red to yellow to white. It finally becomes cold dark matter.

33. P3 4.2 The life history of a star similar in size to our sun Nebular Gravity draws atoms together, releasing energy Protostar Gravity draws atoms together, releasing energy star heats up but does not shine, Main Sequence star White dwarf Protostar Red giant Nebular Star The star shines during fusion of hydrogen to helium for billions of years; outward radiation pressure is balanced by inward pull of gravity. Red giant Most of Hydrogen has been used, now helium fuses to make carbon, unused hydrogen is ejected to the surface, cools and appears red. Whitedwarf Fusion stops, gravitational collapse occurs, star heats up and changes colour from red to yellow to white. It finally becomes cold dark matter.

34. P3 4.2 The life history of a star several times larger than our sun White dwarf massive star Protostar Super red giant Super nova Nebular Super Nova: Fusion stops, gravitational collapse occurs, star heats up and changes colour from red to yellow to white. After further collapse it explodes as a supernova! (Outshines a galaxy for several weeks) Neutron Star: The explosion compresses the core into very densely packed neutrons. If the original star was more massive a black hole would be created. (The gravitational field is so strong that not even light can escape from it.)

35. P3 4.2 The life history of a star several times larger than our sun White dwarf massive star Protostar Super red giant Super nova Nebular Super Nova: Fusion stops, gravitational collapse occurs, star heats up and changes colour from red to yellow to white. After further collapse it explodes as a supernova! (Outshines a galaxy for several weeks) Neutron Star: The explosion compresses the core into very densely packed neutrons. If the original star was more massive a black hole would be created. (The gravitational field is so strong that not even light can escape from it.)