1. 12-1 Notes - Stars
Chapter 12, Lesson 1

2. Stars
Stars are balls of gas, mostly hydrogen, that produce light by nuclear reactions in their cores.

3. Layers of the Sun (outside - in)4. 3. 2. 1.

4. Layers of the Sun (outside - in)
Corona
2,000,000 OC
can only be seen during a solar eclipse.

5. Layers of the Sun (outside - in)
Chromosphere
5,000-10,000 OC
can only be seen during a solar eclipse.

6. Layers of the Sun (outside - in)
Photosphere
5,000 OC - 8,000 OC
this is the layer we get our light from on Earth

7. Layers of the Sun (outside - in)
Core
5,000,000 OC to 100,000,000 OC
where energy is produced through nuclear fusion
has enough fuel to last 10 billion years (currently 5 billion years old)

8. Other Features of the Sun
                                                                                                                                                                                                       
Sunspots – areas of gas that are cooler
Prominences – loops that link sunspot regions
Solar Flares – explosions of gas that have been heated to millions of degrees Celsius.

9. Features of the Sun

10. Features of the Sun

11. Star Types Stars vary in diameters, masses, and surface temperatures.
Our Sun is a medium-sized star with a surface temperature of about 5800 OC.

12. Star Types

13. Star Types Properties of Different Types of Stars Type Diameter
(1=Sun’s dia.)
Mass
(1=Sun’s mass)
Surface
Temp. (K)
Sun 1
5,800 OC
6, K
Kelvin is one of the three best-known scales used to measure temperature, along with Fahrenheit and Celsius.
Each unit on this scale, called a Kelvin rather than a degree, is equal to a degree on the Celsius scale.
There are no negative numbers on the Kelvin scale, as the lowest number is 0 K.

14. Star Types Properties of Different Types of Stars Type Diameter
(1=Sun’s dia.)
Mass
(1=Sun’s mass)
Surface
Temp. (K)
Supergiant
100x – 1,000x
8x -17x
Variable

15. Star Types Properties of Different Types of Stars Type Diameter
(1=Sun’s dia.)
Mass
(1=Sun’s mass)
Surface
Temp. (K)
Supergiant
100x – 1,000x
8x -17x
Variable
Red Giant
10x – 100x
1x – 4x
3,000 – 4,000

16. Star Types Properties of Different Types of Stars Type Diameter
(1=Sun’s dia.)
Mass
(1=Sun’s mass)
Surface
Temp. (K)
Supergiant
100x – 1,000x
8x -17x
Variable
Red Giant
10x – 100x
1x – 4x
3,000 – 4,000
Main
Sequence
0.1x – 15x
0.1x – 60x
2,400 – 50,000

17. Star Types Properties of Different Types of Stars Type Diameter
(1=Sun’s dia.)
Mass
(1=Sun’s mass)
Surface
Temp. (K)
Supergiant
100x – 1,000x
8x -17x
Variable
Red Giant
10x – 100x
1x – 4x
3,000 – 4,000
Main
Sequence
0.1x – 15x
0.1x – 60x
2,400 – 50,000
White Dwarf
0.01x
0.5x – 1.44x
6,000 – 100,000

18. Star Types Properties of Different Types of Stars Type Diameter
(1=Sun’s dia.)
Mass
(1=Sun’s mass)
Surface
Temp. (K)
Supergiant
100x – 1,000x
8x -17x
Variable
Red Giant
10x – 100x
1x – 4x
3,000 – 4,000
Main
Sequence
0.1x – 15x
0.1x – 60x
2,400 – 50,000
White Dwarf
0.01x
0.5x – 1.44x
6,000 – 100,000
Neutron Star
0.00x
variable

19. Scale of Earth, the Sun, Rigel, VY Canis Majoris 3:02

20. Star Distances A light-year is the distance light travels in one year:
9,500,000,000,000 (9.5 trillion) km

21. Star Distances

22. Star Distances

23. Star Composition Stars can only be studied by the light they give off.
Spectroscopes are instruments used to study light, and figure out what elements are in a star.

24. Star Composition Light leaves star.
Light enters Earth’s cool atmosphere.
Light passes through a prism to form a spectrum (rainbow).

25. Star Composition
Dark lines (absorption lines) form along the rainbow because the cooler gases absorb certain wavelengths.
Each element absorbs only certain wavelengths.
Absorption lines help astronomers identify elements in stars, and this lets us know how old they are.

26. Star Composition

27. Star Composition

28. Star Composition

29. Star Temperature
Heated metal goes from red to yellow to white.

30. Star Temperature Star color depends on temperature.
EVERYTHING gives off electromagnetic radiation.

31. Star Temperature The wavelength depends on temperature.
cooler temperatures = longer wavelengths
higher temperatures = shorter wavelengths

32. Star Temperature
The temperature of a star is indicated by the color it glows.

33. Oh Boy, Another F's Gonna Kill Me.
Star Temperature
Oh Boy, Another F's Gonna Kill Me.
The Harvard Stellar Classification System
Type of Star
Color
Surface Temp (oC) O
Blue
Above 25,000 B
Blue-White
10,000 – 25,000 A
White
7,500 – 10,000 F
Yellow-White
6,000 – 7,500 G
Yellow
5,000 – 6,000 K
Orange
3,500 – 5,000 M
Red
Below 3,500

34. Star Brightness A star’s brightness depends on two things:
energy given off
distance

35. Star Brightness Astronomers use 2 ways to define star brightness:
apparent magnitude
absolute magnitude

36. Star Brightness
Apparent magnitude is how bright the star appears from Earth

37. Star Brightness
Absolute magnitude is how bright the star appears at a standard distance of 32.6 light years from Earth (10 parsecs).
Luminosity is measured by how much energy in joules is released per second (1 J/s = a watt)

38. Star Brightness

39. Hertzsprung-Russell Diagram
All known stars are plotted on this graph.
x-axis: temperature
y-axis: luminosity (absolute magnitude)

40. Hertzsprung-Russell Diagram
Main sequence
90% of stars are found in this region, a diagonal, curved line
this is where stars spend most of their life cycle before they start to die

41. Hertzsprung-Russell Diagram
The remaining stars fall into one of three other groups:
Red giants
Supergiants
White dwarfs

42. Star Classifications

43. Star Classifications

44. H-R Diagram 1:34

45. If you know the temperature of any star, what else can you infer about that star?
A its size
B its location in the galaxy
C its color
D its age

46. The apparent brightness of a star depends on what two things?
A magnitude and distance
B distance and temperature
C distance and absolute brightness
D absolute brightness and temperature

47. A light-year is a unit of ____. A time B temperature C brightness
12.1 Stars
A light-year is a unit of ____.
A time
B temperature
C brightness
D distance

48. As a star increases in absolute magnitude, it appears ____ on Earth.
A larger
B hotter
C brighter
D more dense

49. The average distance between Earth and the Sun is called a(n) ____.
A light-year
B astronomical unit
C angstrom
D solar unit

50. A star that is blue in color is ____ than a star red in color.
SCI 4.d
A star that is blue in color is ____ than a star red in color.
A hotter
B cooler
C larger
D smaller