Task #1
Use the technique described in the lab web page to calculate the distance to each star, and type your answer in the “Distance (light years)” column below:

|Star # |Spectral Class |Parallax |Distance |Absolute Magnitude |
| | |(in milli-arc-seconds) |(In Light years) | |
|1 |M5 |34 |97.71 |11.8 |
|2 |A0 |6 |553.67 |0.7 |
|3 |F0 |120 |27.69 |2.6 |
|4 |F5 |67 |49.59 |3.4 |
|5 |O5 |895 |3.72 |-5.8 |
|6 |B0 |77 |43.15 |-4.1 |
|7 |G5 |332 |10.01 |5.1 |
|8 |K5 |54 |61.53 |7.3 |
|9 |K0 |12 |276.84 |5.9 |
|10 |B5 |503 |6.61 |-1.1 |
|11 |A5 |89 |37.33 |2.0 |
|12 |G0 |753 |4.42 |4.4 |

Task #2
What do you think? Is there a relationship between a star’s temperature and its true brightness? If so, how do you think the temperature is going to be related to the true brightness?

There is a direct relationship between a star's temperature and its true brightness. True brightness is measured by how hot the star is.

Task #3
For each star in the table above, use the table on the web page to fill in the “absolute Magnitude” column.

Task #4
Print out the H-R Diagram graph on the last page of this document (below). Use a pen or pencil to plot the true brightness (absolute magnitude) and the temperature (spectral class) of the 12 stars in the chart on page 1 (the first star is done for you). Answer the following: Does a pattern emerge? If so, describe it.

Task #5
Draw a smooth line that passes through (or close to) each dot. NOTE: do NOT make a zig-zag line by connecting the dots – draw a nice flowing smooth line. Label that line the “Main Sequence”.

Task #6
Using the HR-diagram you just created, estimate the absolute magnitude of the following two stars. NOTE: Do so by finding the spectral class along the bottom of the chart (a B3 is about half-way between B0 and B5) then slide your finger straight up until you hit the main sequence line you just drew. Finally, slide your finger to the left, and estimate the value of the absolute magnitude when you hit that scale.

A B3 star:
A G8 star:

Task #7
To make your HR diagram complete, add the following “freak” stars to your HR diagram:

spectral class absolute magnitude

K0 0.5 M0 -0.5

B0 8.5 label this star a “White Dwarf”

Task #8
With all the answers typed in appropriately above, save this document to your hard drive. It is called HR.doc. You can re-name it if you want. Then, attach this document on the Vista web page and click “submit”. NOTE: I realize that I will not see, or be able to grade, the HR-diagram you printed and plotted and labeled. In the past I had students mail them to me, but that’s a hassle, and you can’t answer the above questions correctly unless you made the diagram correctly. If you want, buy a nice frame for the diagram and put it on your wall. (just kidding)

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Label these stars “Red Giants”

star #1

H-R Diagram

Absolute Magnitude

Dim

Bright

Spectral Class

Cool & Red

Hot & Blue

O5

B0

B5

A0

A5

F0

F5

G0

G5

K0

K5

M0

M5

12-

11-

10-

9-

8-

7-

6-

5-

4-

3-

2-

1-

0-

-1-

-2-

-3-

-4-

-5-

-6-

-7-

O5

B0

B5

A0

A5

F0

F5

G0

G5

K0

K5

M0

M5