Physical Science 112: H. Tahsiri

Motion of the Sun

* The Sun also appears to rise in the east and set in the west due to the Earth's rotation.
* However, the Sun moves relative to the stars:
* The Sun moves eastward relative to the stars by about 1° per day.
* The Sun oscillates north/south (within 23°.5 of the celestial equator) over a period of one year.
* The ecliptic is the Sun's path among the stars.
* It is simply the projection of the Earth's orbital plane onto the celestial sphere.

Diurnal Path of the Sun

* The Sun's diurnal path varies during the year.
* Time above horizon depends on where it is relative to the celestial equator.
* Equinoxes occur when the Sun crosses the equator (about 21 March and 21 September).

* Days and nights have equal length, exactly 12 hours.
* Dates known as the solstices occur when Sun is farthest from the celestial equator. Summer solstice occurs around 21 June in the northern hemisphere, and winter solstice occurs around 21 December.

The Zodiac

* The Sun's motion on the ecliptic carries it through a group of constellations called the zodiac.