Chapter 3: Moon Phases and Eclipses

Seasons

Divisions of the year marked by changes in weather patterns and daylight hours, influenced by the tilt of Earth's axis as it orbits the sun and the angle of sunlight

Lunar Phase Cycle

The changing appearance of the Moon as it orbits Earth, transitioning from new moon to full moon and back in about 29.5 days.

Near Side of the Moon

The side of the Moon that constantly faces Earth due to synchronous rotation, with different features than the far side.

Far Side of the Moon

The hemisphere of the Moon that is not visible from Earth due to synchronous rotation. It remains hidden from direct view.

Umbra

The fully shaded inner region of a shadow cast by an opaque object, where no direct light reaches.

Penumbra

The partially shaded outer region of a shadow cast by an opaque object, where light is partially blocked. It is less dark than the umbra.

Penumbral Eclipse

A lunar eclipse where the moon passes through the Earth's penumbral shadow, causing a subtle darkening on part of the moon's surface.

Annular Solar Eclipse

A type of solar eclipse where the Moon covers the center of the Sun, creating a "ring of fire" effect.

Nodes

the two points where the orbit of a celestial body intersects the plane of observation. They are known as the ascending and descending _____.

Saros Cycle

A period of approximately 18 years, 11 days, and 8 hours after which the Sun, Earth, and Moon return to the same relative positions.

North Celestial Pole

The point in the sky directly above Earth's North Pole. It is the center of rotation for all stars in the Northern Hemisphere.

South Celestial Pole

The point in the sky directly above the South Pole on Earth. Stars in the Southern Hemisphere appear to rotate around this point.

Celestial Equator

Imaginary circle in the sky directly above Earth's equator. Divides the celestial sphere into northern and southern hemispheres.

Circumpolar Constellations

star patterns that never set below the horizon from a specific location. They appear to rotate around the celestial pole.

North Circumpolar Zone

Region of the sky surrounding the North Celestial Pole where stars never set below the horizon, visible all year in the Northern Hemisphere.

South Circumpolar Zone

Region of the sky visible from the southern hemisphere, never sets below the horizon. Contains constellations like Crux and Centaurus.

Precession

Motion of Earth's axis, causing a gradual change in the orientation of the celestial poles. It completes a full cycle approximately every 26,000 years.