Proper Motion Demo's and Exercises

Proper Motion Simulator

Take a look at the Proper Motion Simulator at the University of British Columbia Astronomy 311 Website. To get to the simulations page, click on the blue object below the picture of the Earth in the left-hand frame, and from there, select the "Proper Motion" Demo. Try to use the demo to answer the following questions.

1. When the Proper Motion applet has loaded, try running it for the different Asterisms and Constellations provided (vocabulary quiz: what is the difference between a constellation and a asterism?). Note that most stars have relatively small proper motions, but a few have very large proper motions.
2. What does a star's proper motion tell us about the actual space motion of the star. Specifically, does a star with a large proper motion have to have a larger space motion with respect to the solar system than a star with a smaller proper motion? What other piece (or pieces of information must we have, besides a stars proper motion, in order to figure out its complete motion in space (i.e. its velocity) with respect to the solar system?

The Hipparcos Parallax Catalog

The Hipparcos Satellite measured accurate parallaxes for 120,000 stars, down to an apparent magnitude of approximately V=12.4. Besides measuring the parallax of these stars, astronomers also measured the proper motion of the stars. Take a look at their catalog of the 150 stars in the Hipparcos catalog with the largest transverse velocities. Use this table to try and answer the following questions. ( Note: The parallax angles given in these tables are in milliarcseconds (i.e. 1/1000's of an arcsecond, and the proper motions are given in millarcseconds per year).

1. Look at the data for the star with the largest transverse velocity. Use the data given in the table (parallax and proper motion) to calculate the transverse velocity of the star in km/s (Note that the third from the last column in the table gives the transverse velocity in km/s, so you can check your answer).
2. The star with the largest known proper motion is Barnards star, which has a proper motion of 10326.93 milliarcseconds per year. Is Barnard's star listed in the table of the 150 largest transverse velocities? If not, why not? Look up Barnard's star in the table of the 150 closest stars in the Hipparcos Catalog. How does its transverse velocity compare with those of the stars in the 150 largest transverse velocities table?

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