Assignments 2 & 3: Hertzsprung-Russell Diagram

Due: Before 5 pm on Thursday October 19, 2006

Assignment #2

Table 1: Twenty Brightest Appearing Stars

Name	Spectral Class	Visual Luminosity	Distance (light years)
Sirius	A1V	23.5 Suns	2.7
Canopus	F0Ib	1,510 Suns	30
Rigel Kentaurus	G2V	1.56 Suns	1.3
Arcturus	K2III	115 Suns	11
Vega	A0V	55 Suns	7.7
Capella	GIII	166 Suns	14
Rigel	B8Ia	46,000 Suns	~430
Procyon	F5IV-V	7.7 Suns	3.5
Betelgeuse	M2Iab	14,000 Suns	~430
Achernar	B5V	219 Suns	20
Hadar	B1III	3,800 Suns	91
Altair	A7IV-V	11.5 Suns	5
Acrux	B1IV	3,470 Suns	125
Aldebaran	K5III	105 Suns	16
Spica	B1V	2,400 Suns	77
Antares	M1Ib	5,500 Suns	125
Pollux	K0III	41.7 Suns	33
Fomalhaut	A3V	13.8 Suns	7.1
Deneb	A2Ia	50,000 Suns	460
Mimosa	B1IV	6,030 Suns	~140

1. Plot the above stars on the form. Note that you are using a logarithmic scale for the vertical axis. The spectral class of a star (the designation of O,B,A,F,G,K,M in the Table ) is a measure of the surface temperature of a star. The relationship between the spectral class and temperature of a star is given in detail in Topic 4, subsection Spectral Classification in the Webnotes (see also Table 17.2 of the text, Page 449, for a less complete description). The Spectral class for Rigel Kentaurus is G2 V. The G is the overall spectral type while the "2" means that Rigel Kentaurus falls ~20 % of the way between G and K. Roughly, what is the temperature of Rigel Kentaurus? The Roman Numeral "V" is the Luminosity class of the star.

What is the surface temperature of Betelgeuse? What is the surface temperature of Sirius?

2. Fill in the following table:

Table 2: Twenty Brightest Stars Grouped by Distance from Earth

Distance Range	Luminosity Interval
	>10,000	5,000 - 10,000	1,000 - 5,000	100 - 1,000	10 - 100	1 - 10
>250 pc
100-250 pc
75-100 pc
25-50 pc
0-25 pc

Based on the data, what do you infer is the most common type of star in our Galaxy? Are bright stars more common than faint stars? Explain the logic you used.

Assignment #3

Table 3: Thirty Nearest Stars

Name	Spectral Class	Visual Luminosity	Distance (parsecs)
Sun	G2V	1 Suns	0.00048
Proxima Centauri	M5	0.00006 Suns	1.30
Alpha Centauri	G2V	1.6 Suns	1.3
Barnard's Star	M5V	0.00045 Suns	1.8
Wolf 359	M8V	0.00002 Suns	2.4
Lalande 21185	M2V	0.0055 Suns	2.5
UV Ceti	M6V	0.00006 Suns	2.6
Sirius	A1V	23.5 Suns	2.7
Ross 154	M5V	0.00048 Suns	2.9
Ross 248	M6V	0.00011 Suns	3.2
epsilon Eridani	K2V	0.30 Suns	3.3
Ross 128	M5V	0.00036 Suns	3.4
61 Cygni	K5V	0.082 Suns	3.4
epsilon Indi	K5V	0.14 Suns	3.4
Gem 34	M1V	0.0061 Suns	1.1
Luyten 789-6	M6V	0.00014 Suns	3.4
Procyon	F5IV-V	7.65 Suns	3.5
Sigma 2398	M4V	0.0030 Suns	3.5
Lacaille 9353	M2V	0.013 Suns	3.6
G51-15	MV	0.00001 Suns	3.6
Tau Ceti	G8V	0.45 Suns	3.6
BD + 5o1668	M5	0.0015 Suns	3.8
Lacaille 8760	M0V	0.028 Suns	3.8

3. Plot the above stars on your Hertzsprung-Russell diagram (use a different color or symbol for this set of stars to differentiate it from the previous set of stars plotted).

4. Compare and contrast the stars added to your latest Hertzsprung-Russell diagram to the stars you plotted from Table 1.

5. Which star is larger, Betelgeuse or Lacaille 9353? Explain how you used your HR diagram to deduce your answer. How much larger is Betelgeuse than Lacaille 9353?