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.
- 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.
- 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).
- 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).
- 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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