Earth’s Luna: The Moon

2160 miles

2160 miles

Size of moon in diameter

Moon

• It only has a trace of hydrogen, helium, neon, and argon atoms, along with other traces in even lesser quantities. It’s all, or mostly all, made of solid rock.

New Moon

The beginning of the monthly lunar cycle, or lunation.

Waxing Crescent

The moon’s bright areas are getting bigger. This phase happens as the Moon moves away from the Sun–Earth line while orbiting Earth.

Quarter Moon

As the Moon moves around its orbit, it reaches a point where the Earth–Moon line is at right angles to the Earth–Sun line.

Waxing Gibbous

When the illuminated part of the Moon that we can see grows larger than the quarter (half) Moon but is still smaller than the full Moon.

Full Moon

When the Moon is on the far side of its orbit, opposite the Sun in the sky, the lunar hemisphere that faces Earth is fully lit.

Last Quarter

The moon appears as a quarter moon again after a Full moon.

waning crescent

As the Moon nears the line between Earth and the Sun, it becomes a ______ Moon.

Synodic Month

The period of time over which the lunar phases change from the new Moon to the next new Moon, which averages 29 days, 12 hours, and 44 minutes.

Supermoon

It occurs when there is a full Moon at the same time that the Moon is at the closest point (perigee) in its orbit around Earth.

Bluemoon

It looks like other full Moons, and it’s not blue in color. It’s just a bit rare, as in the common expression “once in a blue moon.”

Moon Illusion

It occurs when you watch the Moon rising above the horizon. It seems to most viewers that the Moon looks bigger then than it does a few hours later when the Moon is high in the sky.

Lunar Eclipse

It occurs when a full Moon is exactly on the line from the Sun to Earth.

Lunar Occultation

A phenomenon that happens as the Moon moves across the background stars while orbiting Earth, it sometimes eclipses a bright star.

Immersion

The star disappears behind the moon.

Emersion

The star comes out from behind the Moon.

Asteroidal Occultation

Event when an asteroid passes in front of a star.

Impact Craters

All craters and basins on the moon.

Lunar Highlands

The larger, bright areas in the Man in the Moon, which are heavily cratered areas.

Lunar Soil

Consisting of fine rock dust, covers the surface of the Moon.

Central Peaks

Mountains of rubble thrown up in the rebound of the lunar surface from the effects of a powerful impact.

Lunar mountains

The rims of large craters or impact basins, which may have been partly destroyed by subsequent impacts.

Rays

Bright lines formed by powdery debris thrown out from some impacts.

Giant Impact Theory

The Moon consists of material blasted out of the mantle of Earth by a huge object — with up to three times the mass of Mars — that struck young Earth with a glancing blow.