Name:______Date:______Period:_____

Graphing Stars

Hertzsprung-Russel Diagram

Background:

In 1911 Ejnar Hertzsprung compared data about the temperature and brightness of stars, and plotted his findings in a graph. In 1913 Henry Norris Russell made similar plots. Together their graphs make up the Hertzsprung-Russel Diagram.

On the graph, Absolute Magnitude indicates how bright a star would be if they were all the same distance from Earth. Absolute Magnitude is plotted on the vertical axis with brighter stars on the top. Surface Temperature is plotted along the horizontal axis. The highest temperatures are on the left side of the graph, and the cooler temperatures are on the right. For example, Red Giants are both cool and bright, so they appear in the upper right. A White Dwarf is faint and hot, so they appear in the lower left. Most stars in our galaxy are in mid-life, so they appear on a diagonal line called the main sequence.

Procedure:

Plot the sample stars listed in the table on the back of this paper.

Questions:

  1. Which side of the graph are all of the reddish stars on? Do they have a relatively high or low temperature?
  1. Which side of the graph are the bluish stars on? Do they have a high or low temperature?
  1. Using the data table, which star is the brightest?
  1. Using the data table, which star is the least bright?
  1. What do we call the diagonal line formed by most of the stars on the graph?
  1. Add a new star to your graph with a temperature of 3500˚C and an absolute magnitude of -6. Circle this star with your pen. What color should it be? What type of star is it?
  1. Which star is a white dwarf? How can you tell?
  1. Draw an arrow pointing to the sun. What is it’s temperature like compared to other stars?

Star Name / Temp ˚C / Absolute Magnitude / Color
Alderbran / 4000 / -0.7 / Red-orange
Algol / 10,200 / -0.2 / Blue
Alpha Centauri A / 5800 / +4.4 / Yellow
Alpha Centauri B / 4800 / +5.8 / Orange
Altair / 8800 / +2.2 / Green-blue
Antares / 3400 / -5.1 / Red
Barnard’s Star / 3100 / +13.2 / Red
Betelgeuse / 3300 / -5.6 / Red
GX Andromeda / 3400 / +10.4 / Red
Kruger 60 / 3200 / +11.9 / Red
Procyon / 6500 / +2.6 / Yellow
Proxima Centauri / 3000 / +15.5 / Red
Regulus / 10,400 / -1.7 / Blue
Sirius / 9600 / +1.4 / Blue-white
Sirius B / 10,000 / +11.2 / Blue-white
Sol (our Sun) / 5800 / +4.9 / Yellow
Tau Ceti / 5000 / +5.8 / Yellow-orange
UV Ceti / 2900 / +16.0 / Red
Vega / 10,000 / +0.5 / Blue-white
Wolf 359 / 2900 / +16.7 / red

9.What is the difference between absolute magnitude and apparent magnitude?

10. What is one way that astronomers are able to measure the distance to stars?

11.What is a Binary star? What property does it help astronomers determine?

Absolute Magnitude / -6
-4
-2
0
+2
+4
+6
+8
+10
+12
+14
+16
11,000 / 10,000 / 9000 / 8000 / 7000 / 6000 / 5000 / 4000 / 3000
Temperature