1. Chap. 24-1
Notes: Stars

2. Constellations

3. What are Constellations?
An apparent pattern of stars seen by viewers that seems to travel together across the night sky.
* named after animals, mythological characters, or familiar objects.

4. Early Greek astronomers named many of the constellations.

5. Orion – The hunter

6. Orion

7. Orionids meteor shower (Oct. 20)

8. Taurus – The Bull

9. They are not really groups of stars!
In most cases the stars in a constellation are not actually together in space!

10. Modern astronomers have divided the sky into 88 constellations.

11. Circumpolar Constellations
Constellations that trace daily circles around the North Star(POLARIS).
They never move below the horizon.
Move in counterclockwise direction.
Visible year-round.

12. Florida’s Circumpolar View
Most of U.S.
Florida’s View

13. Five Circumpolar Constellations
Ursa Major, the Big Bear (includes the Big Dipper)
Ursa Minor, the Little Bear
Cassiopeia, the Queen of Ethiopia
Cepheus, the King of Ethiopia
Draco, the Dragon

14. Asterisms
Asterism -A small group of stars that forms a visible pattern but is not an official constellation.
Examples:
Big Dipper
Summer Triangle
Orion's Belt
Summer Triangle

15. Ursa Major – The Great Bear
A circumpolar constellation.
Contains an asterism called the “big dipper”
Pointer stars shows north star! (Polaris)

16. Star Brightness

17. Magnitude
Refers to the brightness of a star.

18. 3 factors affect a stars brightness
1) Temperature 2) Size 3) Distance from Earth

19. Apparent Brightness (apparent magnitude)
How much light we receive from the star.

21. Absolute Brightness (absolute magnitude)
How much light the star is actually giving off.

22. Distance vs Brightness
Two stars of equal size and temp. but at different distances… the furthest is the dimmest.

23. Temp. vs. Brightness

24. Size vs. Brightness

25. Sometimes a small, HOT star is just as bright as a large, COOL star.

26. Light-Year (ly) The DISTANCE that light travels in one year.
* used to measure distance to stars & galaxies.
* Light travels 300,000 Km/sec or about 9.5 trillion Kilometers in a year

27. Polaris (the North Star)
The light we currently see from the North Star was actually emitted in the year 1583.

28. Proxima Centauri * about 4.2 light-years away
The closest star to the Earth after the Sun.
* about 4.2 light-years away

29. Thought to be part of a triple-star system.
Proxima Centuri is a red dwarf star.
Thought to be part of a triple-star system.

30. Parallax
The apparent shift in the position of an object when viewed from two different positions.
* a method used to measure the distance to a star

31. Parallax – good for nearby stars.

32. Ways that Stars vary: 1. size
2.composition
3.Temperature
4.color
5. mass
6.brightness.

33. Differences in temperature of stars
determined by it’s color.
* Blue or Blue-white 35,000 oC
* White ,000 oC
* Yellow ,000 oC
* Red-orange ,000 oC
* Red ,000 oC
* Brown ,000 oC

34. Size Differences

35. Sizes of Stars
List is from largest to smallest diameter. Super Giant Giant Medium Dwarf Neutron

36. What are Stars Made of?
The composition of a star is determined by studying its spectrum.
Instrument = Spectrograph (prism)

37. A star’s spectrum is like a fingerprint
No two stars have the same spectrum!

38. Common Elements of a Star
Hydrogen - 72%
Helium - 27%
Oxygen - <1%
Carbon - <1%
Iron - <1%
Neon - <1%
Magnesum - <1%
Nitrogen - <1%

39. The End