Asteroid is a smaller rocky or metallic object orbiting the sun. Only a few are round. Most are irregular shaped and between the orbits of Mars and Jupiter.
Astronomy is the study of space and galaxies, stars, planets, moons, comets and other celestial bodies found in space.
Astronomical Unit (1 au) is equal to the distance between the sun and earth which is equal to about 150,000,000 km or 90 million miles.
Axis is an imaginary line through earth that earth rotates around.
Celestial Object is any natural thing outside earth’s atmosphere including stars, planets, moons, comets etc.
Celestial Dome is an imaginary overhead dome that is a model representing the night sky as seen by an observer from one location.
Celestial Sphere is similar to the dome but totally encircles the earth, so it is a model of the night sky as seen from anywhere on earth.
Comet is a small icy object orbiting the sun in a very oval path. Has a tail made as it vaporizes into gases.
Day is the time for earth to rotate once on its axis. Days for other planets are not the same amount of time.
Eclipse is one celestial object casting a shadow on another.
Ellipses are closed curves centered around 2 fixed points called foci (they are actually shaped like ovals).
Expanding Universe is the idea that the galaxies are spreading out.
Galaxy is system of stars, cosmic dust and other celestial objects that are held together as a group by gravity.
Gravity is a force that draws any two objects, anywhere, towards each other. Gravity changes due to the mass of the two objects and the distance between their centers.
Inertia is the tendency of objects to stay in the same kind of motion that they are already in. This force opposes gravity to keep satellites in their orbits and not come crashing down.
Meteor (shooting star) is a small solid object falling from space that burns as it passes through earth’s atmosphere.
Meteorite is is a meteor or part of one that is on Earth’s surface.
Month is the time for the moon to revolve once around earth.
Moons are natural satellite orbiting a planet. The Moon is Earth’s satellite.
Moon Phase is the portion of the moon that appears to be lit as seen from Earth. It cycles from new moon to full moon and back during a period of about a month.
Orbits are the elliptical shaped paths that satellites follow through space as they go around their primary.
Planet is the largest “non-star” object that revolves around a star.
Primary is the object that a satellite is orbiting around.
Revolution is movement in a circular or elliptical orbit around a fixed point or primary.
Rotation is the movement of spinning on an axis.
Satellites are objects revolving around a fixed point or primary. Some are natural like planets or moons others are man-made like space stations or T.V. transmitters.
Solar System is the group of celestial bodies includes the sun, planets, moons, comets, asteroids and anything else that revolves around the sun, due to the gravitational pull of the sun.
Stars are celestial objects that shine due to the light energy that is given off by nuclear reactions within the star. They are hot, gassy bodies. The sun is the closest star and the only one in our solar system.
Universe is the sum total of all things that exist within, between and beyond all of the galaxies. It includes matter, time, energy and space.
Year is the time it takes the earth to revolve once around the sun. Years for other planets are not the same amount of time.