Astronomy Terms

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.

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Solar wind is a continuous stream of mostly hydrogen and helium that flows outward from the sun in all directions. It does everything from disrupt GPS signals to create the aurora borealis.

By Mark Mancini

So much of our cosmological history starts with the much-discussed Big Bang, but what led up to that cataclysmic moment? And did time even exist back then?

By Robert Lamb & Patrick J. Kiger

Scientists are still trying to figure out the essence of dark matter. If they do, will it lead only to greater understanding, or can we develop new technologies?

By Patrick J. Kiger

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Everyone knows that nothing travels faster than the speed of light, but how does the speed of dark compare? Read on to find out!

By Bambi Turner

If you have a theory that potato chips are making you fat (with the proof being your expanding waistline), you've just used two scientific terms in a very unscientific way.

By Beth Brindle

You've heard of the big bang, of course, but do you have any idea as to what was happening during that massive flurry of activity billions of years ago?

By Robert Lamb

Every day, astronomers unravel a little more of the universe's inner workings, but the jury is still out on 95 percent of its contents.

By Robert Lamb

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

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

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.

Astrogeology is the science that applies the principles of geology to the study of solid bodies of the solar system other than the earth.

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Transit, in astronomy, is the passage of one celestial body across the disc (face) of a larger, more distant body, or across the observer's meridian.

Astrophysics, the application of the theories and techniques of modern physics to astronomy.

Azimuth, the horizontal direction of an object, measured clockwise in degrees, minutes, and seconds of arc from true north or south along the theoretical horizon.

Bolometer, an instrument used to measure infrared, or heat, radiation. The bolometer is essentially a very sensitive thermometer.

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Chronometer, a timepiece that is exceptionally accurate. Traditionally, the term refers to the marine chronometer, a rugged mechanical instrument used at sea to keep time for navigational purposes.

Cosmogony, the study of the origin and development of the universe as a whole and of the individual bodies that compose it.

Day, in astronomy, the average length of time between successive noons. Noon is defined as the instant when the sun is highest in the sky.

Double Star, a pair of closely-spaced stars that to the unaided eye usually appear as a single star.

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Epoch, in chronology (timekeeping), a point in time, such as 302 B.C. or October 30, 1936, or 7:34 A.M.

Hourglass, a device for measuring time. In its usual form it consists of two cone-shaped or oval glass receptacles joined by a narrow neck.

Interferometer, an instrument that uses the interference patterns formed by waves (usually light, radio, or sound waves) to measure certain characteristics of the waves themselves or of materials that reflect, refract, or transmit the waves.

Magnitude, in astronomy, a unit of measurement of the brightness of stars. The scale of magnitude extends from negative numbers (for example, the minus first magnitude) for very bright stars to positive numbers (for example, the fourth magnitude) for dimmer ones.

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Midnight Sun, a name given the sun when it can be seen at midnight during the Arctic or Antarctic summer.

Minute, a unit for measuring both time and space. As a unit of time, a minute is 60 seconds, or 1/60 of an hour.