Moon
A natural satellite that revolves around a planet.
Lunar craters
Depressions in the Moon formed when asteroids and comets hit it.
Lunar plains
Large, dark flat areas on the Moon believed to be craters formed by meteorite impact that then filled with volcanic lava.
Lunar rays
Streaks of light-colored material extending from craters on the Moon.
Lunar rill
A narrow trench or valley on the Moon.
Lunar fault
A break in Moon's crust along which rocks move.
Synodic month
Time between full or new moons; 29.5 days
Sidereal month
Time for moon to return to same position relative to stars (27.3 days).
New moon
Moon phase that occurs when the Moon is between Earth and the Sun, at which point the Moon cannot be seen because its lighted half is facing the Sun and its dark side faces Earth.
Waxing phase
Amount of light reflected is increasing.
Waning phase
Amount of light reflected is decreasing.
Gibbous moon
When the size of the illuminated portion of the moon is greater than half but not a full moon.
Full moon
Phase that occurs when all of the Moon's surface facing Earth reflects light.
First quarter
Waxing Moon phase in which one-half of the Moon's lighted side can be seen from Earth. (right side illumined)
Last quarter
Waining Moon phase in which one-half of the Moon's lighted side can be seen from Earth. (left side illuminated)
eclipse
The total or partial blocking of light of one celestial body by another.
Umbra
The darkest and smallest part of the shadow.
Total solar eclipse
A complete blocking of the sun. Occurs when you are standing in the moon's umbra.
Penumbra
The part of the shadow surrounding the darkest part.
Partial solar eclipse
Only part of the sunlight is blocked by the moon. Occurs when you are standing in the moon's penumbra.
Annular eclipse
Happens if the moon happens to be too far from Earth for its disk to completely hide the sun. An observer would see a bright run around the dark Moon.
Total lunar eclipse
An eclipse in which the Moon becomes fully covered by Earth's umbral shadow.
Lunar eclipse
The blocking of sunlight to the moon that occurs when Earth is directly between the sun and moon.
Partial Lunar eclipse
When the Moon passes through the Earth's penumbra.
Tides
The regular rise and fall of the ocean's surface influenced by the moon's gravity pulling on earth.
Spring tides
When the sun, moon, and earth are aligned, the pulling forces are combined to produce the highest and lowest tide, happens twice a month.
Neap tides
Tides when the moon is not aligned with the sun, resulting in less extreme tides.
Mercury and Venus
No Moons
Earth
1 Moon
Mars
2 known Moons
Comets
Large clumps of ice, dust and frozen gases that travel around the Sun in long elliptical orbits.
Haley's Comet
A comet named after the scientist who discovered it and it comes around earth every 76 years.
Shoemaker levy
This comet broke up into several comets and were pulled right into Jupiter by it's gravity.
Asteroids
Rocky metallic objects that orbit the sun but are too small to be considered a planet.
Meteors
When a meteoroid entered the Earth's Atmosphere.
Meteoroid
A meteor in space before it enters Earth's atmosphere.
Meteorites
A meteoroid that passes through the atmosphere and hits Earth's surface.
H-R diagram
A diagram that shows the relationship between a star's surface temperature and absolute magnitude.
H-R diagram vertical axis
Absolute magnitude
H-R diagram Horizontal axis
Surface Temperature
Binary stars
When only two stars are gravitationally bound together and orbit a common center of mass.
Globular clusters
A large spherical cluster of gravitationally bound stars usually found in the outlying regions of a galaxy.