Name: ______________________________
Unit 5 – Stars and Galaxies
STAR PROPERTY
LAB PROCEDURE – 107 pts.
Instructions:
In order to complete all items in this lab, it will be useful for you to bring with you to your
lab station classroom notes, diagrams, and any additional handouts provided to you by
the instructor. Remember, you will not be turning in this procedure sheet, but rather a
typed formal lab report document. See WS #9 – Lab Report Format – for all details.
A total of 15 points comes from every lab report for the following pages: title page, introduction and
objective, procedure and materials, and conclusion. All data related to the procedural steps and lab
questions should be documented in the results portion of the submitted lab report.
MATERIALS:
 Graph Paper
 Colored Pencils
 Ruler
 Figure 1 – Stars of Leo, attached
 Figure 2 – Stars of Leo, attached
 Table 1
PROCEDURE:
Part I – Building Your Diagram (57 pts.)
1.
Set up your graph paper landscape (long-ways) in the following fashion: a box with the bottom xaxis labeled “Temperature (Kelvin)”, the top x-axis labeled “Spectral Type”, the right y-axis
labeled ‘Absolute Magnitude (Mv)” and the left y-axis labeled “Luminosity Ratio To Sun (L/L®)”.
Label the top of your diagram, “[Last Name] H-R Diagram”.
2.
In order to label your graph appropriately, you will need to plot the Sun first. See step 4 below to
understand how you will be plotting the star’s on your H-R Diagram. The Sun’s luminosity ratio is
obviously 1. Other marks on your “Luminosity Ratio To Sun” axis should go in increments of 10 2
across from the corresponding absolute magnitudes. Use examples from the PowerPoint H-R
Diagrams provided in class as a basis for your labeling.
3.
The “Absolute Magnitude” axis should go in increments of 5, beginning with +15 at the bottom of
your graph and working your way up to -10 (increasing brightness with lower number values).
The Sun’s absolute magnitude (Mv) is +4.8 and should be very close to 5 on your graph.
4.
The “Spectral Type” axis, starting at the top left should go in order from hottest class to coolest
class. The “Temperature” axis does not need to be labeled in specific increments just use the
following information and align it accordingly with the “Spectral Type” axis:
O  60,000 K – 30,000 K
B  30,000 K – 10,000 K
A  10,000 K – 7500 K
F  7500 K – 6000 K
G  6000 K – 5000 K
K  5000 K – 3500 K
M  3500 K and below
#47
5.
Plot all “Bright Stars” and “Near Stars” on your newly constructed H-R Diagram, with the data
from below, using open circles. The diameter of the circles should be based upon the following:
Ia/Ib  2 cm.
II/III/IV  1.0 cm.
V/VI  0.5 cm.
VII  0.25 cm.
6.
These need to be open circles because you will color them in based on their spectral type:
O  dark blue
B  medium-blue
A  light blue
F  light yellow
G  yellow
K  yellow-orange
M  red
7.
Upon completion of the creation of your H-R Diagram you will include it in the results section for
Part 1 of your submitted lab report.
BRIGHT STARS DATA
STAR
NAME
Sirius A
Sirius B
Canopus
Alpha
Centauri A
Alpha
Centauri B
Arcturus
Vega
Capella A
Capella B
Rigel A
Procyon A
Procyon B
Achernar
Beta Centauri
Betelgeuse
SPECTRAL
TYPE &
LUMINOSITY
CLASS
A1V
B8VII
F0II
ABSOLUTE
MAGNITUDE
(Mv)
STAR
NAME
SPECTRAL
TYPE &
LUMINOSITY
CLASS
A7V
K5III
B1V
ABSOLUTE
MAGNITUDE
(Mv)
+1.4
+11.3
-5.5
Altair
Aldebaran A
Crucis A
G2V
+4.4
Crucis B
B1IV
-3.9
K1V
+5.7
Antares A
M2Ib
-5.3
K2III
A0V
G8III
K0III
B8Ia
F5V
-0.3
+0.6
+0.4
+0.2
-6.8
+2.7
Spica
Pollux
Fomalhaut A
Deneb
Regulus A
Adhara
B2IV
K0III
A3V
A2Ia
B7V
B2Ib
-3.5
+1.1
+1.7
-7.0
-0.5
-4.1
F0VII
B3V
B1III
M2Ia
+13.0
-2.8
-4.6
-6.1
Castor A
Castor B
Shaula
Bellatrix
A1V
A2V
B2IV
B2III
+1.3
+2.3
-5.1
-2.7
+2.2
-0.6
-4.1
NEAR STARS DATA
STAR
NAME
SPECTRAL
TYPE &
LUMINOSITY
CLASS
G2V
ABSOLUTE
MAGNITUDE
(Mv)
STAR
NAME
+4.8
M6V
+15.0
Lalande 21185
M2V
+10.5
Ross 154
Ross 248
M4V
M6V
+13.1
+14.8
Groombridge
34 A
Lacaille 9352
Tau Ceti
Epsilon Eridani
Luyten’s Star
Ross 128
61 Cygni A
61 Cygni B
Epsilon Indi
K2V
M3V
M4V
K5V
K7V
K5V
+6.2
+12.0
+13.5
+7.5
+8.3
+6.9
Barnard’s Star
Lacaille 8760
Kapteyn's Star
Kruger 60 A
Kruger 60 B
Wolf 359
Sun
Proxima
Centauri
ABSOLUTE
MAGNITUDE
(Mv)
Struve 2398 A
SPECTRAL
TYPE &
LUMINOSITY
CLASS
M3V
Struve 2398 B
M4V
+12.0
M2V
+10.3
M2V
G8V
+8.7
+5.7
M4V
M2V
MIV
M3V
M4V
M7V
+13.2
+8.7
+10.9
+11.8
+13.5
+16.7
+11.2
Part 2 – Spectroscopic Parallax (25 pts.)
Finding the distances to stars based upon their spectral type and luminosity class is known as
spectroscopic parallax (even though no parallax determination is involved). This method is neither easy
nor exact; however, it has proved to be one of the best ways to learn about very distant stars. The first
part of this method involves determining the star's spectral type and luminosity class. Astronomers can
determine a star's spectral type based on the absorption lines in the spectrum of the star. The hottest
stars show strong hydrogen lines and some helium lines. Spectral type A stars have predominately only
hydrogen lines. As stars get cooler, more lines will appear as heavier elements [for example, calcium (Ca),
and iron (Fe)] recapture their electrons. The singly ionized calcium atoms (Ca II) are especially strong in
spectral type G stars. Spectral type K stars have very weak hydrogen lines but strong iron lines and similar
heavy elements. The width of a line can be used to determine an approximate luminosity for a star. For a
given element, supergiant stars will have narrow lines and dwarf stars will have broad lines. You will need
to obtain Table 1, which lists the 14 stars in the constellation Leo in order of their apparent magnitude
(mv). Seven of the stars have already been classified, with their absolute magnitudes (Mv) and distances
also calculated. Your mission for this part of the lab is to fill in missing details on Table 1 for the other
seven stars and include it in the results section for Part 2 of your submitted lab report.
1.
Figures 1 and 2, attached to this lab procedure sheet, show a series of standard spectra used to
classify stars (Fig. 1) and the seven stars in Leo that have already been classified as well as the
seven that you need to classify (Fig. 2). First, take a look at the 7 stars in Leo that have already
been classified, and compare each to the corresponding standard spectrum. Use the examples
given to guide you in classifying the remaining seven stars in Fig. 2.
Note: because of the need to keep the image sizes small, some image quality had to be
sacrificed. Note, too, that there is a shift in some of the spectra. Let the line patterns and
strengths guide you in your classification. Also, the standard spectra are for luminosity
class V only. Do not worry about being extremely accurate -- this is not an exact science!
2.
Enter your best guesses of the spectral types in column 3 of Table 1. Luminosity classes for the
stars are already given.
3.
Assign each star an absolute magnitude based on its spectral class and luminosity class. You
must use an H-R Diagram from the PowerPoint examples to do this or find one having spectral
types along with luminosity class groups plotted on the diagram. Fill in column 6 of Table 1.
4.
Calculate the distance to each of the seven stars based upon the absolute magnitude from
spectroscopic parallax using the Magnitude-Distance Formula.
5.
For the seven unclassified stars, fill in Table 1 for the distances determined from the parallax
values, using the Trigonometric (Stellar) Parallax Formula, d = 1/p
LAB QUESTIONS (10 pts.)
1.
Why can’t we use trigonometric (stellar) parallax to determine the distances to all stars?
2.
Differentiate between apparent visual magnitude and absolute visual magnitude.
3.
The H-R Diagram is sometimes called a color - magnitude diagram. Why is this (or why is this
not) an appropriate name?
4.
What is the diagonal band of stars, running from top left to bottom right of the H-R Diagram?
5.
Which stage includes roughly 90% of all normal stars?
6.
Does our Sun have a final resting place on the H-R Diagram? Explain your answer.
7.
Explain the width for the Balmer lines of Hydrogen, when looking at a stars’ spectrum, for mainsequence stars, giant stars, and supergiant stars.
8.
Identify the luminosity classes of stars.
9.
Describe the 3 types of binary star systems and how we observe/study each one.