1. Real Stars!

Here is a catalog of real stellar data; we are going to make some Hertzprung-Russell Diagrams out of it. The dataset is the Yale Trigonometric Parallax Dataset, and the data is as follows:

column 1: star ID number
column 2: apparent V magnitude
column 3: observed B-V color
column 4: observed parallax (in arcsec)
column 5: uncertainty in parallax (in milliarcsec)

First, make a Hertzprung-Russell diagram using the entire dataset. That is, make a plot with B-V color on the x-axis, and ABSOLUTE magnitude on the y-axis. Things to remember in your plot:

Label your axes!
Don't use really big point sizes! You are going to plot over 6000 stars on this plot, so use small dots or it'll all run together...
You are astronomers, which means your H-R diagram should have bright stars AT THE TOP and blue stars TO THE LEFT.
Use intelligent axis limits -- don't let your software autoscale the plot so that all the stars end up scrunched up on one side of the plot.

Those last two points are important; if you dont take care, your plot will end up looking like this silly thing and who wants that?

In fact, to make sure you get it right, this is what your plot should look like. Just to show you dont need fancy data analysis software to do this, here's a version I made using M$ Excel.

Now, on your HR diagram, label the various types of stars (main sequence stars, red giants, white dwarfs, etc) and also indicate where the Sun would appear.

And then make 3 more H-R diagrams:

One using stars with parallax uncertainties smaller than 100 millarcsecs
One using stars with parallax uncertainties smaller than 50 millarcsecs
One using stars with parallax uncertainties greater than 100 milliarcsecs

Explain why the different parallax error limits lead to the differences you see in the 4 H-R diagrams you've made. Make sure to pay attention to the kinds of stars that show up, the numbers of stars that show up in different regions (ie how many red giants vs how many red dwarfs, for example), and the properties of the main sequence.

2. The Mission of the USS Asinus

We are going to explore a young star cluster. Unfortunately, your trustworthy Captain forgot to stop by the Blexxon Dilithium Fuel Station on the last mission, and so we are low on fuel. We only have a range of 1200 (make it 1100) parsecs. We have one of three possible clusters to go visit: Jenny's cluster, the Ohtz Swarm, and Laungheer 213.

You captain did manage to take some quick images of each cluster, getting apparent V magnitudes and B-V colors, but he got distracted watching the Galactic Bowl game (us vs the evil aliens known as the Hoarsflize) and the data is pretty poor.

Your job is to use the data for each cluster to plot a color-magnitude diagram for each cluster and then decide which cluster we can actually get to. You will probably also find Appendix E of your book very helpful. Naah, I don't like their main sequence table, use this one instead.

Here are data for the three clusters:

Astr 221 Homework #5 -- Due Nov 4

1. Real Stars!

2. The Mission of the USS Asinus