1. Characteristics of Stars

2. What is a Star? A star is a large collection of matter that emits huge amounts of energy The sun is the most important star to us as it is at the centre of our solar system

3. Distances in Space The closest star to our solar system is Alpha Centauri It is 40 trillion km away A light year is the distance light travels in one year (9.46 trillion km) Alpha Centauri is 4.3 light years away

4. Life cycles of Stars

5. How are these stars different?

6. Classifying Stars Stars are classified based on: – Colour – Temperature – Size – Brightness

7. Colour/Temperature The colours of stars tell us something about their temperature A relatively COOL star glows RED A very HOT star glows BLUISH-WHITE or BLUE

8. ColourTemperature Range (°C) Example Blue25 000 – 50 000Zeta Orionis Bluish-White11 000 – 25 000Rigel White7500 – 11 000Vega or Sirius Yellowish- White6000 – 7500Polaris Yellow5000 – 6000Sun or Alpha Centauri Orange3500 – 5000Arcturus Red2000 – 3500Betelgeuse

9. Size Stars also range in size from being SUPERGIANT to DWARF.

10. Brightness of Stars Just over 2000 years ago, a Greek astronomer Hipparchus decided to classify stars based on their brightness: – Brightest  First Magnitude – Faintest  Sixth Magnitude

11. Two ways to look at magnitude: APPARENT magnitude is the brightness as it APPEARS to us ABSOLUTE magnitude is the actual amount of light given off by a star at a standard distance

12. Plotting the Properties of Stars Astronomers plot the properties of stars on a diagram that compares brightness with surface temperature and colour.

13. Constellations A constellation is a group of stars that form a pattern We recognize 88 constellations today Most familiar constellations are named after characters in Greek mythology

14. The Big Dipper A part of the constellation Ursa Major (big bear) Resembles an old fashioned plow and the shape of a ladle

15. The Little Dipper Part of the constellation of Ursa Minor (little bear) Tip of the little dipper’s handle is the brightest star, Polaris (the north star)

16. Can you see it?

17. Bootes Has the unmistakable shape of a kite Located by following the handle of the Big Dipper The brightest star is Arcturus Arcturus is 100x brighter than the sun

18. Can you see it?

19. Cassiopiea One of the most recognizable shapes among constellations A distinct W, formed by five main stars

20. Can you see it?

21. Orion One of the most distinct features is his belt made of three stars Two key stars are Betelgeuse and Rigel

22. Can you see it?

23. Canis Major Represents one of the dogs that accompanied Orion the Hunter. Dominated by the lead star Sirius (popularly known as the dog star)

24. Can you see it?

25. A Map of the Sky