The Sun and Other Stars

1. The Sun and Other Stars

2. The Cone Nebula

4. Features of the Sun • The Sun is a large ball of gas • The surface layer of the Sun is called the photosphere • It is about 6000 °C • Sunspots are dark areas of the sun where there is strong magnetic activity • Watching the movement of sunspots, scientist have discovered the Sun rotates • It rotates faster at the equator than at the poles (doesn’t rotate like the Earth or other planets do)

6. Solar Flares • When magnetic fields explode and send out charged particles into space • Solar wind – Fast-moving charged particles sent out by the Sun • Solar storms can cause damage to satellites and other electronic equipment on Earth • Can also result in auroras – charged particles from the Sun charge gases in the atmosphere and lead to different colours in the sky at the North and South Poles

9. Why is the Sun Important • The Sun is needed for all life on Earth • Solar energy causes the winds and ocean currents • It provides energy for photosynthesis and is the main force behind all of earth’s weather and climate • The Sun sends out a lot of different types of energy like: • Microwaves, radio waves, x-rays, gamma rays. • The energy that reaches the surface of Earth are as visible light and infrared radiation (heat)

10. Other stars • Luminosity – A star’s total energy output per second • Some stars have been found that are more than 400,000 times more luminous than the Sun!! • Absolute magnitude – What magnitude we would observe the star to have if it was place 32.6 light-years from Earth • The Sun would have an absolute magnitude of 4.7 (not very bright at all)

11. Other stars • Stars have different colours – blue, blue-white, yellow, orange, red • The colour of the star can be used to guess the temperature of the star. • The Sun is yellow and is about 6000 C at the surface • Blue stars are hotter – up to 35,000 C at the surface • Red stars are colder – about 3300 C at the surface

13. How Big is Our Sun Compared to Other Stars? • Video

14. The Mass of Stars • Binary stars are two stars that orbit each other • Star masses are measured in solar masses– The Sun is that standard and is 1 solar mass • Some stars are over 100 solar masses – this means that they are 100 times more massive than the Sun • A Hertzsprung-Russel (H-R) diagram – is a graph that compares stars colour and absolute magnitude or luminosity

17. Star Classification • Main sequence – A band of stars on an H-R diagram that runs diagonally from upper left (bright- hot stars) to lower right (dim, cool stars) • 90% of all stars (including our Sun) are main sequence stars.

18. How stars Evolve • Stars may last for millions to billions of years, but eventually their fuel runs out • Stars end up as either a white dwarf, a neutron star or a black hole when they run out of fuel • What they turn into depends on their starting mass

19. Low-mass stars • Low mass stars like red dwarfs have less mass than the Sun • They take up to 100 billion years to burn up their hydrogen • When they run out of fuel, they become white dwarfs – small, dim and hot star

21. Intermediate-Mass Stars • Like our Sun • Use up hydrogen in about 10 billion years • Core collapses (caves-in) when fuel is used up • Pressure increases and the star gets bigger • It becomes a red giant. The sun will become a red giant and will be as big as the orbit of Mars • Eventually they will shrink down to become a white dwarf

23. High-mass Stars • Stars that are 12 or more solar masses • Use up there fuel much faster and therefore die much faster • Do to higher temperatures and pressures, are able to form heavier elements up to iron. • First they will expand to red supergiants • When the core collapses, an explosion is sent out called a supernova • Supernova’s blow off the outer part of the star and can be million of times brighter than the star was

24. Did you know that… All the iron in your blood came from supernovas!! In fact most of the atoms that make up your body started in the stars at one time in the past!! Supernovas were first discovered in 1987 by Canadian astronomer Ian Shelton from the University of Toronto

27. Neutron stars and Black Holes • If a star starts with a mass of 12-15 solar masses  it will become a neutron star after its supernova • If a star starts with a mass of more than 25 solar masses it will become a black hole • Neutron stars are about 20-30 km in diameter • Some neutron stars spin up to 30 times per second, these are called pulsars

28. Neutron stars and Black Holes • Black holes have so much mass and gravity that light cannot escape. • Black holes were predicted to exist before they were even discovered • Since you can’t see a black hole, scientists look for gravitational effects caused by the black hole • Dr. Tom Bolton of the University of Toronto was the first person to identify a black hole in 1972. • Supermassive black holes are thought to exist at the center of every galaxy

30. New Discovery Newly discovered black hole is 17 billion times the mass of the sun, may be biggest ever found • Found in a small galaxy called NGC 1277 • (one quarter the size of our Milky Way)