The 14 Stars Nearest Earth the 15 Brightest Stars Seen from The

PLOTTING THE H-R DIAGRAM

Problem: Is the Sun an Average Star?

Materials: Graph Paper, Colored Pencils (RED/BLUE)

Procedure: 1. Use the graph attached with this activity. 2. Plot the temperature and brightness for the 14 nearest stars in RED pencil. 3. On the same graph, use a blue pencil to plot the data for the 15 brightest stars provided. 4. Answer questions 1-6.

Data and Observations: The 14 Stars Nearest Earth Star Temp. Brightness Distance Star Temp. Brightness Distance (Sun = 1) (Sun = 1) (K) (LY) (K) (LY) Sun 5,600 1 0.00002 Sirius B 10,700 0.008 8.6 Proxima 5,800 1.3 4.3 Luyten 726-8A 2,700 0.00006 8.9 Alpha Centauri A 4,200 0.36 4.3 Luyten 726-8B 2,700 0.00004 8.9 Alpha Centauri B 2,800 0.00006 4.3 Ross 154 2,800 0.0004 9.4 Barnard’s 2,800 0.00044 5.9 Ross 248 2,700 0.00011 10.3 Wolf 359 2,700 0.00002 7.6 Epsilon Eridani 4,500 0.30 10.7 Sirius A 10,400 23.0 8.6 Ross 128 2,800 0.00033 10.8

The 15 Brightest Stars Seen from the Northern Hemisphere Temperature Brightness Distance Star Constellation Month Observed (K) (Sun = 1) (LY) Aldebaran Taurus Dec/Jan/Feb 4,200 90 53 Altair Aquila July/Aug/Sept 8,000 10 16.5 Antares Scorpius May/June/July 3,400 4,400 400 Arcturus Bootes April/May/June 4,500 90 36 Betelgeuse Orion Jan/Feb/March 3,200 17,000 500 Capella Auriga Dec/Jan/Feb 5,900 150 47 Deneb Cygnus July/Aug/Sept 9,900 40,000 1,400 Fomalhaut Pisces Austrinus Oct/Nov/Dec 9,500 14 23 Pollux Gemini Feb/March/April 4,900 3,300 29 Procyon Canis Minor Feb/March/April 6,500 7.6 11.4 Regulus Leo March/April/May 20,000 92 84 Rigel Orion Jan/Feb/March 11,800 40,000 800 Sirius Canis Major Feb/March/April 10,000 23 8.6 Spica Virgo April/May/June 21,000 1,900 260 Vega Lyra July/Aug/Sept 10,700 60 26 PLOTTING THE H-R DIAGRAM Question and Answer:

1. How does the brightness and temperature of the sun compare to the brightest stars in the Northern Hemisphere?

2. How does the sun compare to the closest stars to it?

3. Which are probably the more common type of stars in the Milky Way, the brightest or the suns nearest neighbors?

4. How does the sun compare to a “common” star?

5. What relationships exist between the stars in the two lists for this activity and the four main types of stars (Main Sequence, Giants, Dwarfs, Neutron Stars)?

6. Based only on the information provided in this activity, if all the stars in the Milky Way were plotted on the H-R Diagram, where would most stars be located? Where the “average” star should be plotted?

PLOTTING THE H-R DIAGRAM 100,000

10,000 SUN = 1 = SUN

1,000

100

0.1

0.01

0.001

0.0001 STAR MAGNITUDE (BRIGHTNESS) MAGNITUDE STAR

0.00001

000

9,000

6,500

13 25 TEMPERATURE (K)