Astronomy terms are used to describe the various phenomena in space. In this section you can learn what every astronomy term means and how it helps us to better understand the cosmos.



Summer, the season of the year occurring between spring and autumn. Astronomically, summer in the Northern Hemisphere lasts from about June 21 to September 23; in the Southern Hemisphere, from about December 22 to March 21.

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  • Meteorite

    Meteorite, a meteor that reaches the earth's surface. Meteors are naturally occurring objects that enter the earth's atmosphere from space, traveling at high speed. See more »

  • Satellite, Artificial
    Satellite, Artificial

    Satellite, Artificial, a man-made object that orbits the earth, the moon, the sun, or any other celestial body. See more »

  • Seasons

    Seasons, the four divisions of the year, called spring, summer, autumn (or fall), and winter. See more »

  • Sundial

    Sundial, a device used to tell time by the sun. Nearly every sundial has two basic parts: a pointer, called a style or gnomon, which casts a shadow; and a numbered dial on which the shadow falls to show the hour. See more »

  • What is a light year?
    What is a light year?

    A light year is a way of measuring distance. That doesn't make much sense because "light year" contains the word "year," which is normally a unit of time. Even so, light years measure distance. See more »

  • Year

    Year, a unit of time. It is based on the time it takes the earth to make one revolution around the sun. See more »

  • Aberration of Light
    Aberration of Light

    Aberration of Light, a phenomenon in which a star or other celestial body, as viewed from the earth, appears to be slightly displaced from its true position. See more »

  • Albedo

    Albedo, in astronomy, the reflecting power of a celestial body that is not self-luminous. See more »

  • Andromeda Galaxy
    Andromeda Galaxy

    Andromeda Galaxy, a spiral galaxy that is larger than the Milky Way (the galaxy to which Earth belongs) but similar to it in structure, and the closest to ours. See more »

  • Astrogeology

    Astrogeology, the science that applies the principles of geology to the study of solid bodies of the solar system other than the earth. See more »

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