Constellations and Stellar Distances
Student Instructions
Introduction: Your instructor will give you an introduction to stellar parallax, or you may look this up on the internet at http://en.wikipedia.org/wiki/Parallax#Stellar_parallax . In this exercise, you will access a database used by professional astronomers and look up the parallax measurements for the seven main stars in the well-known constellation Orion. Using these measurements, you will be able to calculate the distances to these stars and make a chart of the relative distances on the worksheets provided. You can then make a determination as to whether or not these seven stars are actually close to each other, as they appear in the sky.
Example: Here is an example of the calculations you will do, using the parallax measurement for Sirius, the brightest star in the sky. SIMBAD gives us a measurement of 379.21 mas (milliarcseconds).
First convert to arcseconds:
Calculate distance in parsecs:
Calculate distance in light years:
Instructions:
1. Access the SIMBAD database at http://simbad.harvard.edu/Simbad .
2. Click on “Query by identifier.”
3. Enter the name of the first star from your worksheet and click on the “submit” button.
4. The first section of the next page is labeled “Basic Data.” Look for the parallax measurement (in mas) at the bottom of this section. (It is usually the last line of this section.) Record this data on your worksheet.
5. Calculate the distance to the star in pc and LY. Record this on your worksheet.
6. Repeat these steps for the remaining stars on your worksheet.
7. On Worksheet 2, draw a horizontal line for each star, to represent the distance the star is from our solar system.
8. After you have completed Worksheet 2, consider the following question: Are the main stars in Orion actually close to each other? Write your answer on your worksheet.