Constellation

A constellation is a group of stars visibly related to each other in a particular configuration. In three-dimensional space, most of the stars we see have little relation to one another, but can appear to be grouped on the celestial sphere of the night sky. Humans excel at finding patterns and throughout history have grouped stars that appear close to one another into constellations.

Related Topics:
Star - Configuration - Three-dimensional - Celestial sphere - Night - Sky - Human - Pattern

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An "unofficial" constellation, that is, one that may be widely known but is not recognized by astronomers or the International Astronomical Union, is also called an asterism, such as The Plough (also known in the US as the Big Dipper) and the Little Dipper.

Related Topics:
International Astronomical Union - Asterism - The Plough - US - Big Dipper - Little Dipper

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The stars in a constellation or asterism rarely have any astrophysical relationship to each other; they just happen to appear close together in the sky as viewed from Earth and typically lie many light years apart in space. However, one exception to this is the Ursa Major moving group.

Related Topics:
Earth - Light years - Ursa Major moving group

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The grouping of stars into constellations is essentially , and different cultures have had different constellations, although a few of the more obvious ones tend to recur frequently, e.g., Orion and Scorpius.

Related Topics:
Culture - Orion - Scorpius

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The International Astronomical Union (IAU) divides the sky into 88 official constellations with precise boundaries, so that every direction belongs to exactly one constellation. In the northern celestial hemisphere, these are mostly based upon the constellations of the ancient Greek tradition, passed down through the Middle Ages, and contains the signs of the zodiac.

Related Topics:
International Astronomical Union - Boundaries - Direction - Greek - Middle Ages - Zodiac

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The constellation boundaries were drawn up by Eugène Delporte in 1930, and he drew them along vertical and horizontal lines of right ascension and declination. However, he did so for the epoch B1875.0, which means that due to precession of the equinoxes, the borders on a modern star map (eg, for epoch J2000) are already somewhat skewed and no longer perfectly vertical or horizontal. This skew will increase over the years and centuries to come.

Related Topics:
Eugène Delporte - 1930 - Right ascension - Declination - Epoch - B1875.0 - Precession - J2000

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