ASTRONOMY 206.2 GENERAL ASTRONOMY II
“Solutions” Sheet
Student Name
Laboratory Exercise 15. Cepheids and the Distance Scale
Purpose. To use Cepheid variables to determine the distance to the Small Magellanic Cloud.
Procedure. See Laboratory Manual.
Equipment.

Cepheid light curves and data
Data.
Cepheid
log Period
<MV>
Cepheid
log Period
<MV>
SU Cas
SZ Tau
CV Mon
QZ Nor
V Cen
V367 Sct
DL Cas
0.29
0.65
0.73
0.74
0.74
0.80
0.90
–2.0
–3.1
–3.4
–3.3
–3.4
–3.6
–3.8
S Nor
 Gem
X Cyg
WZ Sgr
SW Vel
SV Vul
0.99
1.01
1.21
1.34
1.37
1.65
–4.0
–4.1
–4.7
–5.1
–5.1
–6.1
Harvard Variable
Magnitudes mv
Brightest
Faintest
Period (days)
log Period
Mean
2019
2035
844
2046
1809
1987
1825
1945
1903
16.8
16.7
16.3
16.0
16.1
16.0
15.6
15.2
15.6
0.35
0.44
0.49
0.56
0.60
0.65
0.79
0.81
0.88
2063
1873
14.7
1.11
843
1954
2060
847
13.8
14.3
13.8
1.22
1.24
1.44
1967
840
11182
13.4
13.6
1.52
1.60
837
1827
1877
13.1
13.1
1.63
1.70
Apparent Magnitude of 10 day Cepheids (log P = 1.0)
mv =
Absolute Magnitude of 10 Day Cepheids (log P = 1.0)
MV =
Distance Modulus of Small Magellanic Cloud, mv – MV
=
–
=
Distance to Small Magellanic Cloud, d
 mv  M V   5 

5

= 10 
_____________________
= 10
_____
= 10
=
Discussion.
Conclusions.
parsecs