Constellations
<p>A <b>constellation</b> is formally defined as a region of the <a href="https://en.wikipedia.org/wiki/Celestial_sphere" title="Celestial sphere">celestial sphere</a>, with boundaries laid down by the <a href="https://en.wikipedia.org/wiki/International_Astronomical_Union" title="International Astronomical Union">International Astronomical Union</a> (IAU). The constellation areas mostly had their origins in Western-traditional patterns of stars from which the constellations take their names.
In 1922 the International Astronomical Union officially recognized the <a href="https://en.wikipedia.org/wiki/88_modern_constellations" title="88 modern constellations">88 modern constellations</a>, covering the entire sky. They began as the 48 classical Greek constellations laid down by <a href="https://en.wikipedia.org/wiki/Ptolemy" title="Ptolemy">Ptolemy</a> in the <i><a href="https://en.wikipedia.org/wiki/Almagest" title="Almagest">Almagest</a></i>. Constellations in the far southern sky are late 16th- and mid 18th-century constructions. 12 of the 88 constellations compose the <a href="https://en.wikipedia.org/wiki/Zodiac_sign" class="mw-redirect" title="Zodiac sign">zodiac signs</a>, though the astronomical positions of the constellations only loosely match the dates assigned to them in <a href="https://en.wikipedia.org/wiki/Astrology" title="Astrology">astrology</a>.
The term constellation can also refer to the stars within the boundaries of that constellation. Notable groupings of stars that do not form a constellation are called <a href="https://en.wikipedia.org/wiki/Asterism_%28astronomy%29" title="Asterism (astronomy)">asterisms</a>. When astronomers say something is “in” a given constellation they mean it is within those official boundaries.
Any given point in a <a href="https://en.wikipedia.org/wiki/Celestial_coordinate_system" title="Celestial coordinate system">celestial coordinate system</a> can unambiguously be assigned to a single constellation (but see <a href="https://en.wikipedia.org/wiki/Argo_Navis" title="Argo Navis">Argo Navis</a>). Many <a href="https://en.wikipedia.org/wiki/Stellar_designation" title="Stellar designation">astronomical naming systems</a> give the constellation in which a given object is found along with a designation in order to convey a rough idea in which part of the sky it is located. For example, the <a href="https://en.wikipedia.org/wiki/Flamsteed_designation" title="Flamsteed designation">Flamsteed designation</a> for bright stars consists of a number and the genitive form of the constellation name.</p>