# Astronomy

How to complete the HR Diagram RMcCord Astro 20
For Attendance Credit, turn in a photocopy of one Notebook page with the Answers below.
For each star, plot points in the graph-space on the HR Diagram provided:
Select a star name from the table of stars.
Find the given temperature on the top horizontal axis of the HR Diagram (as accurately as possible). Lay a ruler
perpendicular to the horizontal axis but crossing it at the temperature you located. NOTE: you may also use the Spectral
Classification on the top horizontal axis; they are equivalent!
Find the absolute Magnitude for the selected star from the table of stars. Find that Magnitude on the right side vertical
axis. Put a small round mark on the graph where the temperature (marked by the ruler) and the Magnitude intersect.
Write a small number next to the mark for the star you are working on.
Repeat this for the list.
From the Lecture Notes and the Textbook, lightly circle the areas for: Main Sequence, White Dwarfs, Red Giants and
Supergiants.
1. Name two stars that are near the Sun in the Main Sequence
2. Name one star that is Main Sequence but at least 4 magnitudes brighter.
3. Name two stars that are Red Giants
4. Name two stars that are White Dwarfs
5. Name two stars that are Supergiants
6. What is the Spectral Class letter of a star at temperature 2400K
7. What is the Spectral Class (letter and number) of a star around 27000K
8. What is the temperature that separates B9 from A0
9. MS, WD, RG or SG, which category is a star with 6000K and M=5
10. MS, WD, RG or SG, which category is a star around 30000K and M=-5
11. MS, WD, RG or SG, which category is a star with 4500K and M=0
12. MS, WD, RG or SG, which category star is Betelgeuse
13. What Spectral Class is star Sirius A ? Sirius B ?
14. About what temperature is Sirius A? Sirius B? Which is absolutely brighter?
15. What Spectral Class is Barnards Star
16. MS, WD, RG or SG, which category would a star be if it were Spectral Class G3 and Magnitude +7

number Name M
spectral
class
1 Sun 5 G2
2 Canopus 3 F0
3 Centauri A 5 G2
4 Procyon A 3 F5
5 Spica 3 B1
7 Procyon B 13 F0
8 Sirius B 11 A0
9 Alnitak 6 O9
10 Crucis 3 B3
11 Sirius A 1 A1
12 Arcturus 0 A2
13 Vega 0 A0
14 Rigel 7 B8
15 Betelgeuse 6 M2
16 Crucis 5 F5
17 Mirfak 5 F5
18 Polaris 5 F8
19 Barnard’s Star 13 M4
20 Aldebaran 1 K5
21 Regulus 1 B7
22 Bellatrix 4 B2
23 Alnilam 6 B0
24 Deneb 7 A2
Selected Stars
Attachments:

hr_diagram_3_page_assignment.pdf

l21_hrdiagram.ppt

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