Searching for Europium using Stellar Spectroscopy
The complete activity is meant to take a full class and maybe even two.
We are going to compare the relative amount of the elements nickel and europium in a couple of stars.
Plotting A Stellar Spectrum
Watch the “HOW TO” video: https://www.youtube.com/watch?v=XkOUVOJrtrQ
- If you haven’t already, copy the data to your Google Drive (use your initials in the file name).
- Highlight the 2 columns of data. Most spreadsheets will assume the left column goes on the x-axis and the right column goes on the y-axis. This data is ready to go since column A is the wavelength in Angstroms and column B is the relative flux or amount of starlight. You can think of this as the brightness of a particular wavelength.
- The easiest way to measure with the plot is if the chart type is set to ‘smooth line’.
- Change the title of the graph to “Star name Spectrum” but use the real star name. 🙂
- Change the y-axis title to Relative Flux or something similar.
- Change the limits on the x-axis and y-axis so just the region with the absorption feature is visible.
- Change the tick marks on the x-axis and y-axis so you can easily read off the plot. I used 0.05 on the y-axis with 4 minor marks and 0.1 on the x-axis with 4 minor marks. I also turned on all the various tick marks.
Determining atomic abundance: Equivalent Width
How to measure equivalent width
- First, count how far down from 1on the y-axis the “bell curve” bit goes and write that in a cell labeled Max Abs or something similar. This is the maximum absorption for this feature.
- Next, in an adjacent cell, hit = to enter a formula and click on the cell where you typed the value for the max absorption and divide that by 2. This is the half-max value.
- We will use the half-max value to count down from 1 on the y-axis to where the curve meets that y-value on both the right and the left. Write down in an empty cell the left wavelength where the curve meets that half-max value and then write down in another empty cell the similar value on the right side of the curve.
- Next, click an empty cell and click = to enter a formula. Be sure to put the difference between the right and left values in parentheses before you multiply by the max absorption.
- This value represents the equivalent width for this spectral feature. This is a numerical way to describe the relative abundance of a particular atom for a star. (Note: this is not the actual number of a particular atom.)
- Repeat for the other stars!
Plotting Spectra with Python and Google Colab
You can also try out some Python coding to plot the stellar spectra using Google Colab Notebook. Give it a try!
CSTA CS Across the Curriculum Talk
UH Research Experience for Teachers 2021 Symposium
The Kepler spacecraft made some incredible discoveries over the years. The planetary system Kepler-11 is very interesting. It is a very compact solar system with 6 planets. Of course, the spacecraft is named for Johannes Kepler who first empirically determined the now famous three laws of planetary motion.
I felt like this small dataset would make a great computational thinking (CT) activity. CT can mean writing programming code or working with a spreadsheet to do some data science or creating or using a model or simulation. The goal is to explore Kepler’s 3rd law of planetary motion.
In the original activity, students linear the data set using Kepler’s 3rd law of planetary motion to determine the mass of the star Kepler-11. Check out the spreadsheet version here. This is meant to be an introductory exercise is working with data in a spreadsheet. Students create a plot and answer questions using some basic skills.
Although the spreadsheet version of the lab worked out pretty well, I decided to make a Desmos calculator version. Students can work with the whole list of planetary data all at once. This is more like a students creating a numerical model to find the mass of the star. Check out the Desmos version here.
Finally I decided to create a version of the Kepler’s 3rd law lab using some Python code in Google Colab. This version uses some standard data science techniques to determine the mass of the central star in the Kepler-11 system. Check out the Google Colab version on my GitHub repository.
This work is licensed under a Creative Commons Attribution 4.0 International License.
Come see either of my CAST 2021 sessions.
Thursday, Nov 11, 2021 2:30 PM – 3:30 PM CST
Location: Sundance 6, Omni Hotel
Session Code: 20068
Friday, Nov 12, 2021 11:00 AM – 12:00 PM CST
Location: 200, Fort Worth Convention Center
Session Code: 5067
September 17, 2021
Link to AP Physics C Syllabus: https://docs.google.com/document/d/1yAmMvMVS5nWjH1msWZ9L39YzWI_HWDih5dVMpy8yRmM/edit?usp=sharing
Link to IB Astronomy Syllabus: https://docs.google.com/document/d/17WB_f9H5FM-uwMnqh-cgnlCYZt2Y9YUCby7oNmj7QQc/edit?usp=sharing
Visit the Google Colab Notebook to learn about my summer 2021 research