Name________________________________Date___________________Period_________

Properties of Stars Lab The Hertzsprung-Russell diagram, or H-R diagram, is a graph in which a star’s temperature is plotted against its absolute magnitude. From such a diagram, other information about a star’s properties and life cycle can be determined. A simplified H-R diagram appears in your textbook. In this lab, you will construct an H-R diagram using data on the 20 stars that are nearest to our sun and the 20 stars that appear brightest in our sky Then you will use the finished diagram and your notes to describe the properties and life cycles of the stars. In the data tables below, the unit used for distance is the parsec. You will need to convert parsecs into light years. 1 parsec is equal to 3.26 light-years (LY). The unit for temperature is the Kelvin (K), or absolute temperature scale.

Purpose: To understand the different properties of stars such as color, temperature and brightness (magnitude) and they relate to the Hertzsprung–Russell diagram. Procedure: 1. Analyze the 20 nearest stars to earth and the 20 brightest star as seen from earth in the data table below. *** In procedure steps 2 and 3, you will graph the stars onto the H-R diagram. The following tips may be useful: • Color and Temperature is on the horizontal axis, absolute magnitude is on the vertical axis. • Notice that the graph lines used to plot temperature are unevenly spaced, and that the number of Kelvins between each line is not constant. Carefully check a star’s temperature and the value of a particular line before plotting each star. • Absolute magnitude (true brightness of a star) decreases as you move up on the H-R diagram.

2. Determine how far away each star is by converting parsecs into light years. 1 parsec = 3.26 light years 3. Graph each star according to its absolute magnitude (brightness) and temperature. Remember there is a direct relationship between star color and temperature. As you plot and graph each star, use color pencils to assign the correct color to each star. Color white stars light blue. 4. First graph the 20 NEAREST STARS then graph the 20 BRIGHTEST STARS as seen from Earth listed in the data table below on the H-R Diagram.

Data : The 20 Nearest Stars to earth Name

Distance (Parsecs)

Alpha Centauri Barnard’s Star Wolf 359 Lalande 21185 Sirius Luyten 726-8 Ross 154 Ross 248 Epsilon Eridani Ross 128 Luyten 789-6 61 Cygni Procyon Epsilon Indi Sigma 2398 BD +43°44

1.31 1.83 2.35 2.48 2.67 2.67 2.94 3.16 3.30 3.37 3.37 3.40 3.47 3.51 3.60 3.60

Tau Ceti CD -36°15693

The 20 Brightest Stars as Seen from Earth Absolute Magnitude

Name

Distance (Parsecs)

5800 2800 2700 3200 10 400 2700 2800 2700 4500 2800 2700 2800 6800 4200 3000 3200

+4.4 +13.2 +16.8 +10.5 +1.4 +15.4 +13.3 +14.7 + 6.1 +13.5 +14.9 +7.5 +2.7 +7.0 +11.1 +10.3

3.64 3.66

5200 3100

+5.7 +9.6

BD +5°1668

3.76

3000

+11.9

Sirius Canopus Alpha Centauri Arcturus Vega Capella Rigel Procyon Betelgeuse Achernar Beta Centauri Altair Alpha Crucis Aldebaran Spica Antares Pollux Fomalhaut Deneb Beta Crucis

2.7 30.0 1.3 11.0 8.0 14.0 250.0 3.5 150.0 20.0 90.0 5.1 120.0 16.0 80.0 120.0 12.0 7.0 430.0 150.0

CD -39°14192

3.92

3500

+8.7

6000

+4.7

Sun

Light Years

Temp (K)

Light Years

Temp (K)

Absolute Magnitude

10,400 7400 5800 4500 10 700 5900 11 800 6800 3200 14 000 21 000 8000 21 000 4200 21 000 3400 4900 9500 9900 22 000

+1.4 -3.1 +4.4 -0.3 +0.5 -0.7 -6.8 +2.7 -5.5 -1.0 -4.1 +2.2 -4.0 -0.2 -3.6 -4.5 +0.8 +2.0 -6.9 -4.6

Conclusion Questions: (answer in complete senetences) 1) Compare the 2 star lists, 20 nearest and 20 brightest. How many stars appear on both the lists? Name them and circle them on the lists.

2) What does your answer to question 1 indicate about the nearest stars? Are the nearest stars also the brightest stars as seen from Earth?

3) A star located in the lower right portion of the H-R diagram is cool and dim. What are the characteristics of a star in the upper left of the diagram? In the upper right?

4) To which group do most of the stars on your diagram belong? (giants, white dwarfs, super giants, main sequence)?

5) According to your diagram, are any of the 20 nearest or 20 brightest stars white dwarf starts? What is the evidence of your answer?

6) Our sun has a temperature of 6000 k and an absolute magnitude of +4.7. To what group does the sun belong?

7) Compare the absolute magnitude and temperature of the sun with those of the other stars in its group. Is our sun a bright or dim star? Hot or cool star?

8) Betelgeuse is 150 parsecs away and has a surface temperature of only 3200K, yet Betelgeuse is one of the brightest stars as seen from earth. What does this indicate about the size of Betelgeuse? Is your answer supported by the location of Betelgeuse on the diagram?

9) On your H-R diagram, there is another star that is plotted near Betelgeuse. What is the name of the star? What kind of stars it is?

10) Compare our sun with the red super giant Antares. Which star is further along in its life cycle? How do you know?

H-R Diagram