The motion of the planets in their orbits can be demonstrated to students by using planetarium software programs.1 These allow time to be sped up so that the relative motions are readily observed. However, it is also valuable to have the students understand the real speed of the planets in their orbits. This paper describes an exercise that gives students a good understanding of real-time motions and then allows other questions to be asked to encourage further understanding of planetary geometry and motion.
Topics
Education
REFERENCES
1.
The Sky, Software Bisque, Golden, CO, is one of many available.
2.
ESSCO charts S0511 and S0512 are available from Sky Publishing Corp., 49 Bay State Road, Cambridge, MA 02138.
3.
I also have the students plot the position of the Moon in its orbit on an Earth centered chart, which I created but I have left out that exercise here. The Moon chart and some questions can be found in the online Appendix B at E-PHTEAH-45-021706 http://ftp.aip.org/cgi-bin/epaps?ID=E-PHTEAH-45-021706.
For more information on EPAPS, see http://www.aip.org/pubservs/epaps.html.
4.
JPL's Horizons website (http://ssd.jpl.nasa.gov/horizons.cgi) provides an ephemeris calculator that is useful for determining the ecliptic longitude and distance of planetary objects.
5.
Note that copyright restrictions prevent the display of the ESSCO charts so this figure was created using the planetary orbital elements and general plotting software. The ESSCO chart has an additional circle outside the rest, which is marked in degrees counterclockwise from the Vernal Equinox. This is used to mark the planet locations each week.
6.
Appendix A can be viewed online at E-PHTEAH-45-021706 http://ftp.aip.org/cgi-bin/epaps?ID=E-PHTEAH-45-021706).
7.
The perimeter of the ESSCO chart has the names of the zodiacal constellations marked in the appropriate directions.
8.
This is a trick question because the orbit of Pluto is way beyond the limits of the Outer Planet Chart.
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© 2007 American Association of Physics Teachers.
2007
American Association of Physics Teachers
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