Moon

The Moon is 2,160 miles in diameter, slightly more than a quarter of the diameter of Earth.
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.
As the Moon nears the line between Earth and the Sun, it becomes a waning crescent 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.
- The totally eclipsed Moon can look a dull orange, an even duller red, or a very dark red.
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.

Earth’s Luna: The Moon

The Moon is 2,160 miles in diameter, slightly more than a quarter of the diameter of Earth.
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.
As the Moon nears the line between Earth and the Sun, it becomes a waning crescent 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.
- The totally eclipsed Moon can look a dull orange, an even duller red, or a very dark red.
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.