Astr 221 Homework #5 -- Due Nov 4
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:
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:
- 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)
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?
- 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.
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
stars, red giants, white dwarfs, etc) and also indicate where the Sun
And then make 3 more H-R diagrams:
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
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.
- One using stars with parallax uncertainties smaller than 100
- One using stars with parallax uncertainties smaller than 50
- One using stars with parallax uncertainties greater than 100
2. The Mission of the USS
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
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
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
Naah, I don't like their main sequence table, use this one instead
Here are data for the three clusters: