The motion of one body around another (e.g. the motion of the planets in their orbit around the Sun).
The action of rotating around an axis or center.
A group of stars forming a recognizable pattern
a unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.4607 × 1012 km (nearly 6 trillion miles).
The apparent magnitude (m) of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere.
a prominent pattern or group of stars, typically having a popular name but smaller than a constellation.
The two stars at the end of the bowl of the Big Dipper, Merak and Dubhe
of a star or constellation visible above the horizon at all times at a specified locality on the earth's surface
the highest point reached by a celestial or other object.
the alternate rising and falling of the sea, usually twice in each lunar day at a particular place, due to the attraction of the moon and sun.
Phases of the moon
an eclipse in which the moon appears darkened as it passes into the earth's shadow.
an eclipse in which the sun is obscured by the moon.
Why do we have seasons?
The Earth's axis is tilted at an angle of 23.5 degrees. This means that the Earth is always "pointing" to one side as it goes around the Sun. So, sometimes the Sun is in the direction that the Earth is pointing, but not at other times. The varying amounts of sunlight around the Earth during the year, creates the seasons.
Planet (include inner planet & outer planet)
a celestial body moving in an elliptical orbit around a star.
any of the planets Mercury, Venus, earth, and Mars, whose orbits lie inside the asteroid belt
Outer: any of the planets Jupiter, Saturn, Uranus, Neptune, and Pluto, whose orbit lies outside the asteroid belt
A system of planets or other bodies orbiting another star
Retrograde motion is motion in the direction opposite to the movement of something else
An astronomical unit (abbreviated as au;other abbreviations that are sometimes used include ㍳, a.u. and ua) is a unit of length now defined as exactly 149,597,870,700 m (92,955,807.3 mi), or roughly the average Earth–Sun distance.
the orbital radius is the distance from the planet to the Sun, or roughly one astronomical unit in the Earth's case (149,598,000 km).
States that the Earth is in the center of all celestial bodies
Sates that the sun is the center of the solar system and all other celestial objects orbit it in perfect circles
a celestial object consisting of a nucleus of ice and dust and, when near the sun, a “tail” of gas and dust particles pointing away from the sun.