Grus (, or colloquially ) is a constellation in the southern sky. Its name is Latin for the crane, a type of bird. It is one of twelve constellations conceived by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman. Grus first appeared on a 35-centimetre-diameter (14-inch) celestial globe published in 1598 in Amsterdam by Plancius and Jodocus Hondius and was depicted in Johann Bayer's star atlas Uranometria of 1603. French explorer and astronomer Nicolas-Louis de Lacaille gave Bayer designations to its stars in 1756, some of which had been previously considered part of the neighbouring constellation Piscis Austrinus. The constellations Grus, Pavo, Phoenix and Tucana are collectively known as the "Southern Birds". The constellation's brightest star, Alpha Gruis, is also known as Alnair and appears as a 1.7-magnitude blue-white star. Beta Gruis is a red giant variable star with a minimum magnitude of 2.3 and a maximum magnitude of 2.0. Six star systems have been found to have planets: the red dwarf Gliese 832 is one of the closest stars to Earth to have a planetary system. Another—WASP-95—has a planet that orbits every two days. Deep-sky objects found in Grus include the planetary nebula IC 5148, also known as the Spare Tyre Nebula, and a group of four interacting galaxies known as the Grus Quartet.
History
The stars that form Grus were originally considered part of the neighbouring constellation Piscis Austrinus (the southern fish), with Gamma Gruis seen as part of the fish's tail. The stars were first defined as a separate constellation by the astronomer Petrus Plancius, who created twelve new constellations based on the observations of the southern sky by the Dutch explorers Pieter Dirkszoon Keyser and Frederick de Houtman, who had sailed on the first Dutch trading expedition, known as the Eerste Schipvaart, to the East Indies. Grus first appeared on a 35-centimetre-diameter celestial globe published in 1598 in Amsterdam by Plancius with Jodocus Hondius. Its first depiction in a celestial atlas was in the German cartographer Johann Bayer's Uranometria of 1603. De Houtman included it in his southern star catalogue the same year under the Dutch name Den Reygher, "The Heron", but Bayer followed Plancius and Hondius in using Grus. An alternative name for the constellation, Phoenicopterus (Latin "flamingo"), was used briefly during the early 17th century, seen in the 1605 work Cosmographiae Generalis by Paul Merula of Leiden University and a c. 1625 globe by Dutch globe maker Pieter van den Keere. Astronomer Ian Ridpath has reported the symbolism likely came from Plancius originally, who had worked with both of these people. Grus and the nearby constellations Phoenix, Tucana and Pavo are collectively called the "Southern Birds". The stars that correspond to Grus were generally too far south to be seen from China. In Chinese astronomy, Gamma and Lambda Gruis may have been included in the tub-shaped asterism Bàijiù, along with stars from Piscis Austrinus. In Central Australia, the Arrernte and Luritja people living on a mission in Hermannsburg viewed the sky as divided between them, east of the Milky Way representing Arrernte camps and west denoting Luritja camps. Alpha and Beta Gruis, along with Fomalhaut, Alpha Pavonis and the stars of Musca, were all claimed by the Arrernte.
Characteristics Grus is bordered by Piscis Austrinus to the north, Sculptor to the northeast, Phoenix to the east, Tucana to the south, Indus to the southwest, and Microscopium to the west. Bayer straightened the tail of Piscis Austrinus to make way for Grus in his Uranometria. Covering 366 square degrees, it ranks 45th of the 88 modern constellations in size and covers 0.887% of the night sky. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "Gru". The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined as a polygon of 6 segments. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 21h 27.4m and 23h 27.1m , while the declination coordinates are between −36.31° and −56.39°. Grus is located too far south to be seen by observers in the British Isles and the northern United States, though it can easily be seen from Florida or San Diego; the whole constellation is visible to observers south of latitude 33°N.
Features
Stars
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