STARS

1. STARS

2. DISTANCES IN THE SOLAR SYSTEM • Our Sun is the closest star to us. • Distances in the solar system are so big that we use a large unit of measurement. • A LIGHT YEAR is the distance light travels in one year.

3. WHAT IS A LIGHT YEAR? Consider the following: • Light travels 300 000 km every second. • There are 31 536 000 seconds in a year Distance = speed x time • Therefore, if we multiply the numbers together, we get 10 trillion km, or 10 000 000 000 000 km!

4. LIGHT YEARS, CONT’D • The closest star to us, Alpha Centauri A , is 4.3 light years away. • This is equivalent to 43 000 000 000 000 km away from us!

5. WHAT IS A STAR? STAR: A collection of matter that emits huge amounts of energy. STARS are classified based on four characteristics: • Colour • Temperature • Size • Brightness

6. Stars glow because they are very hot. The colour that an object glows tells us how hot it is. Cool stars glow red; very hot stars glow blue. COLOUR & TEMPERATURE

7. SIZE OF STARS GIANTS AND DWARFS • When a star begins to reach “old age” the pressure inside runs out as all the hydrogen runs out. • As the star gets older, it swells in size. • Our Sun will become a Red Giant as it runs out of fuel. • When it “dies” it will become a white dwarf. • Our Sun is bigger than 95% of the stars in the Universe. • The Size Of Our World

9. OTHER ASTRONOMICAL STUFF… SUPERNOVA • An enormous explosion when a large star dies. • When all the hydrogen is used up the core collapses • The absence of pressure causes a neutron star or a black hole. • The explosion can be bright enough to see during the day!

11. OTHER ASTRONOMICAL STUFF… NEUTRON STAR • These stars are ten times bigger than our Sun. • It become a dense core of neutrons. • A PULSAR is a type of neutron star.

12. OTHER ASTRONOMICAL STUFF… BLACK HOLE • These are stars thirty times bigger than our Sun. • Small, very dense object with an extremely strong gravitational pull. • Nothing can escape from it; not even light.

14. OUR SUN • The Sun’s energy comes from NUCLEAR FUSION, a reaction that takes place under high temperature and pressure. • Nuclear Fusion

15. OUR SUN The Sun has multiple layers: • Core:Nuclear fusion takes place here, and temperatures can reach 15 million °C. • Photosphere:The surface of the Sun, made up of moving gases; average temperature of 5500 °C. Sunspots occur here.

16. OUR SUN • Chromosphere:the inner atmosphere of the Sun • Corona: The hot outer layer of the Sun; temperatures reach 1 million °C.

17. OUR SUN Other features of the Sun: • Solar Prominence:an explosion of glowing gases from the chromosphere that can last for weeks and reach 40,000 km high. • Solar Flare: Like a solar prominence, but the gases travel into the corona, and last only a few minutes.

19. GALAXIES & STAR CLUSTERS • Galaxy: a collection of gas, dust, and hundreds of billions of stars. • Our Sun is located in the less-populated spiral arm of the Milky Way.

20. GALAXIES & STAR CLUSTERS • There are approximately 400 billion stars in our galaxy. • The majority of the stars are located in the central bulge.

21. Unusual Galaxies • Quasars:Astronomical objects that look like very faint stars, but emit hundreds of times more energy than entire galaxies. • Scientists do not know the reason for the intense light output.

22. STAR CLUSTERS • Star Clusters:groups of stars that are close together and travel as a group (as few as 10 or as many as 1 million). Ex. Pleiades