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A scale for measuring the actual brightness of a star.
The temperature at which the motion of all atoms and molecules stops.
When dust and gas accumulates to bigger bodies.
The point in the orbit of the Moon or other satellite where it is farthest from the Earth.
The angular distance of an object above the horizon.
The apparent brightness of an object in the sky as it appears to an observer on the Earth.
The point in the orbit of a planet or other celestial body where it is farthest from the Sun.
A small rocky body orbiting the sun. Large numbers of these, ranging enormously in size, are found between the orbits of Mars and Jupiter, though some have more eccentric orbits.
A unit of measure equal to the average distance between the Earth and the Sun.
A layer of gases surrounding a planet, moon or star.
A glow in a planet's ionosphere caused by the interaction between the planet's magnetic field and charged particles from the Sun.
An imaginary line through the center of rotation of an object.
The angular distance of an object around or parallel to the horizon from a predefined zero point.
The point in the orbit of a planet or other celestial body where it is closest to the Sun.