Name: ________________________________
Date: _______ Per: _______
Unit Two: Astronomy
Lab Activity: Properties of Stars (Hertzsprung- Russell Diagram)
The Hertzsprung-Russell diagram or H-R diagram is a graph in which a star’s
temperature is plotted against its absolute magnitude (actual brightness of star). 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 (Pages 578 & 579). READ the text and
captions on these pages to understand what the H-R diagram shows. Additionally, use the
website, schoolsobservatory.org.uk, Astronomy, Stars, HR Diagram. In this laboratory you will
use a completed H-R diagram using data from 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 to describe the
properties and life cycles of stars.
The 20 Nearest Stars
Distance Temp
(light-year)
(C)
Alpha Centauri
4.27
5800
Barnard’s Star
5.97
2800
Wolf 359
7.66
2700
Lalande 21185
8.12
3200
Sirius
8.70
10400
Luyten 726-8
8.70
2700
Ross 154
8.28
2800
Ross 248
10.30
2700
Epsilon Eridani
10.76
4500
Ross 128
10.99
2800
Luyten 789-6
10.99
2700
61 Cygni
11.08
2800
Procyon
11.31
6800
Epsilon Indi
11.44
4200
Sigma 2398
11.74
3000
BD +43°44
11.74
3200
Tau Ceti
11.86
5200
CD -36°15693
11.93
3100
BD +5°1668
12.26
3000
CD -39°14192
12.78
3500
Name
Absolute
Magnitude
+ 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
+ 5.7
+ 9.6
+ 11.9
+ 8.7
The 20 Brightest Stars as Seen from Earth
Distance Temp Absolute
(light-year)
(C)
Magnitude
Sirius
8.70
10400
+ 1.4
Canopus
97.80
7400
- 3.1
Alpha Centauri
4.27
5800
+ 4.4
Arcturus
35.86
4500
- 0.3
Vega
26.08
10700
+ 0.5
Capella
45.64
5900
- 0.7
Rigel
815.00
11800
- 6.8
Procyon
11.31
6800
+ 2.7
Betelgeuse
489.00
3200
- 5.5
Achernar
65.20
14000
- 1.0
Beta Centauri
293.40
21000
- 4.1
Altair
16.63
8000
+ 2.2
Alpha Crucis
391.20
21000
- 4.0
Aldeberan
52.16
4200
- 0.2
Spica
260.80
21000
- 3.6
Antares
391.20
3400
- 4.5
Pollux
12.0
4900
+ 0.8
Fomalhaut
22.82
9500
+ 2.0
Deneb
1401.80
9900
- 6.9
Beta Crucis
489.00
22000
- 4.6
Questions:
1. Compare the two star lists above. How many stars appear on both the Nearest Stars list and the
Brightest Stars list? Name them. _______________________________________
________________________________________________________________________
2. What does your answer to question one indicate about the nearest stars? Are the nearest stars also the
brightest stars as seen from Earth? Answer space at top of back page.
2._________________________________________________________________________________
_____________________________________________________________
3. A star located in the lower right portion of the H-R diagram is cool and dim. What are the
characteristics (Temp. and Absolute Magnitude) of a star in the upper left of the diagram? In the upper
right?
Upper left: ______________________________________________________________
Upper right: _____________________________________________________________
4. Refer to pages 578 and 579 of your textbook. To which group does most of the stars on your diagram
belong?
_______________________________________________________________________
5. According to your diagram and the textbook diagram, are any of the 20 nearest or 20 brightest stars
white dwarfs? What is the evidence for your answer?
________________________________________________________________________
6. Our sun has a temperature of 5,800 C and an absolute magnitude of + 4.7. To what group of stars does
the sun belong?
________________________________________________________________________
7. Betelgeuse is 489 light-years away and has a surface temperature of only 3200 K yet Betelgeuse is one
of the brightest stars as seen from Earth. What does this indicate about the size of Betelgeuse? Why is
your answer supported by the location of Betelgeuse on the H-R diagram?
________________________________________________________________________
________________________________________________________________________
8. On your diagram, there is another star that is plotted near Betelgeuse. What is the name of the star and
what kind of star is it?
_______________________________________________________________________
9. Compare our sun with the red supergiant star Antares. Which star is further along in its life cycle?
How do you know?