The Celestial Globe: Ecliptic

This OER was designed by the OU Academy of the Lynx (oulynx.org) in conjunction with the "Galileo's World" (galileo.ou.edu) exhibition at the University of Oklahoma.

Introductory Ecliptic Handout

1. On a celestial globe, find the path of the Sun, or ecliptic.  

Any constellation which contains the ecliptic is called a Zodiac constellation.  The ecliptic is important because where the Sun travels, the planets follow.  Bright stars in zodiac constellations that don’t appear on star charts are wandering planets.

2. Trace the great circle of the ecliptic around the celestial globe.  Identify the constellations of the Zodiac that include the ecliptic.

Early star atlases were based on the great circle of the Sun’s annual path around the sky.  

Celestial “longitude” measures in degrees along the ecliptic.  By convention, the starting point, or 0 degrees of celestial longitude, is a point on the celestial equator called the vernal or March equinox.   

3. Which constellation contains the March equinox?

Celestial “latitude” measures in degrees perpendicular to the ecliptic.

The ecliptic is the year-long path of the Sun against the background of fixed stars.  An equinox is where the ecliptic and celestial equator intersect.  

4.  How many equinoxes can you find?

5. What is the angle between the celestial equator and the ecliptic?

Because the ecliptic and the Earth’s equator do not coincide, celestial latitude and celestial longitude (based on the ecliptic) do not coincide with terrestrial latitude and longitude (based on the celestial equator).

The star atlas of John Flamsteed was the first major atlas to use a grid based not on the ecliptic, but on the Earth’s geographical coordinates. Flamsteed thus introduced the convention now used in modern star atlases of basing star positions on the celestial equator rather than the ecliptic.

Further OER's

Use the following OER's to further explore the Galileo's World exhibition.

• Galileo's World iPad Exhibit Guide, itunes.apple.com/us/book/galileos-world-exhibit-guide/id1032005948?mt=1.
• Galileo's World iTunes U Course, itunesu.itunes.apple.com/enroll/FDS-EYK-MRL.
• Galileo's World website, galileo.ou.edu.

Ecliptic Educational Cluster

We want to create variations on this activity that connect the Ecliptic Activity to a variety of ages. Use the following chart and hyperlinks to find the one to best fit your group.