Cycles of the Sky

Celestial Sphere

A model representing the arrangement of stars with Earth at its center, simplifying the 3-D arrangement for observation.

Constellations

Fixed patterns of stars resembling animals, objects, or mythological figures, not physically related but appearing in specific arrangements from Earth's perspective.

Mnemonic Tools

Ancient constellations likely served as aids for tracking seasons and navigation.

Daily Motion

The apparent movement of celestial objects due to the rotation of the celestial sphere around Earth's celestial poles.

Celestial Equator

An imaginary line aligned with Earth's equator, serving as a reference point for astronomical observations.

Ecliptic

The Sun's apparent path through the stars on the celestial sphere, projected from Earth's orbit.

Zodiac

Twelve primary constellations through which the ecliptic passes, with Ophiuchus as an additional constellation.

Earth's Axial Tilt

The 23.5º tilt of Earth's axis, causing the changing seasons and varying solar altitudes.

Solstices and Equinoxes

Celestial events marking extreme points in the Sun's rising and setting positions, used by ancient civilizations to track time.

Lunar Phases

The Moon's cycle of phases, including new, crescent, quarter, gibbous, and full, occurring over approximately 30 days.

Eclipses

Phenomena occurring when the Sun, Earth, and Moon align, resulting in shadows; includes solar and lunar eclipses.

Solar Eclipse

An event where the Moon blocks the Sun's light from reaching Earth.

Lunar Eclipse

An event where Earth's shadow falls on the Moon, causing it to appear reddish.