The Ecliptic

The ecliptic is the apparent path that the sun follows over the surface of the celestial sphere through the course of the year. Of course the sun is NOT actually moving around through the constellations over the course of the year; the earth is moving around the sun. Since we see the sun from different sides at different times of the year, we have the sun appearing against a different part of the sky as background at different times of year, making it appear to move.

In the early part of ASTR 106, we are more concerned with the way things look than the way they are, and therefore we will continue to talk of the sun as moving, even though it is actually the motion of the earth around the sun that creates the appearance of the sun's motion.

Where the Sun is Day by Day

The apparent motion of the sun through the year is steadily to the east, that is, leftwards across your map. If you look closely directly at the underside of the ecliptic, you will find scale markings and a series of dates. For example if you look at the ecliptic just inside the right edge of your map, you should find the date Sep 25 just underneath the ecliptic. Moving left from that date, you should be able to find Oct 1, and then Oct 10 with associated scale markings on the bottom side of the ecliptic.

The scale mark associated with each date marks the position of the sun on the ecliptic on that particular date. The sun's position is marked at approximately every 10 days through each month of the year.

See if you can find where the sun is on March 30, and then on July 20, and finally on New Year's Day, Jan 1.

(You will also notice some numbers on top of the ecliptic. These mark the position of the sun every ten days through the year, starting at the first day of spring.)

The Origin of the Name

You might wonder about the origin of the name "Ecliptic." The name arises from the fact that the apparent path of the sun among the constellations is closely connected with eclipses of the sun and moon. From the word "Eclipse" we get the name for the sun's path: Ecliptic.