Grus constellation lies in the southern sky. Its name means “the crane” in Latin.
The stars of Grus were once part of the constellation Piscis Austrinus. It was the Dutch astronomer Petrus Plancius who created the constellation Grus from the observations of the Dutch navigators Pieter Dirkszoon Keyser and Frederick de Houtman in the late 16th century.
The constellation first appeared in a celestial atlas in 1603, in Johann Bayer’s Uranometria. In the early 17th century, it briefly went by an alternative name, Phoenicopterus, which means “the flamingo” in Latin.
FACTS, LOCATION & MAPGrus us the 45th constellation in size, occupying an area of 366 square degrees in the sky.
It is located in the fourth quadrant of the southern hemispere (SQ4) and can be seen at latitudes between +34° and -90°.
Grus contains four stars with known planets and no Messier objects. The brightest star in the constellation is Alnair, Alpha Gruis, with an apparent magnitude of 1.74. There are no meteor showers associated with the constellation.
There are no myths associated with the constellation. Grus was one of the 12 constellations created by Dutch explorers in the late 16th century. The only connection the crane has with mythology lies in the fact that it was a sacred bird to the god Hermes.
The constellation was created from stars located to the south of the constellation Piscis Austrinus. The brightest star in Grus is called Alnair, which means “the bright one from the fish’s tail” in Arabic. Similarly, the proper name of Gamma Gruis, Al Dhanab, also means “the tail” in Arabic.
MAJOR STARS IN GRUS
Alnair – α Gruis (Alpha Gruis)
Alnair is the brightest star in the constellation. It has an apparent visual magnitude of 1.74 and is approximately 101 light years distant from the solar system.
Alpha Gruis is either a main sequence star with the stellar classification of B6 V or a B7 IV class subgiant. It has a radius 3.4 times that of the Sun, four times the solar mass, and is about 263 times more luminous. The star’s estimated age is 100 million years.
Alnair is a rapid rotator, with a projected rotational velocity of 215 km/s. Based on the excess infrared emission from the star, it is believed to have a dust disk in its orbit.
The name Alnair comes from the Arabic al-nayyir, which means “the bright one,” from the phrase al-Nayyir min Dhanab al-ḥūt, or “the bright (star) belongs to the tail of the (Southern) Fish (constellation).” The Southern Fish is the English name for the constellation Piscis Austrinus.
Gruid – β Gruis (Beta Gruis)
Beta Gruis is a red giant belonging to the spectral class M5 III. It has a visual magnitude of 2.146 and is 177 light years distant from the Sun. It is the second brightest star in Grus.
The star is classified as a semiregular variable as its luminosity varies in magnitude by about 0.4 over a period of 37 days or longer.
Beta Gruis is one of the stars that used to form the tail of the Southern Fish, and before it became part of the Grus constellation, it was the rear star in the tail of the constellation Piscis Austrinus.
The star has 2.4 times the Sun’s mass and 180 times the solar radius. It is approximately 1,500 times more luminous than the Sun.
Al Dhanab – γ Gruis (Gamma Gruis)
Gamma Gruis is the third brightest star in Grus. It is a giant with the stellar classification B8 III, about 390 times more luminous than the Sun. It rotates pretty rapidly, with a projected rotational velocity of 57 km/s. The star’s name means “the tail” in Arabic, referring to its previous position in the constellation Piscis Austrinus.
Gamma Gruis has an apparent visual magnitude of 3.003 and is approximately 211 light years distant.
δ Gru (Delta Gruis)
Delta Gruis is a binary star in Grus. It is composed of a G7III-type star with an apparent magnitude of 3.97 and a M4.5IIIa class star with a magnitude of 4.17. Under good conditions, both stars are visible to the naked eye.
τ1 Gruis (Tau-1 Gruis, HD 216435)
Tau-1 Gruis is a yellow dwarf of the spectral type G0V. It has a visual magnitude of 6.03 and is 108.58 light years distant from the solar system. An extrasolar planet at least 1.23 the mass of Jupiter was discovered in the star’s orbit in 2002.
Tau-1 Gruis has 1.25 solar masses and is 3.6 times more luminous than the Sun.
Gliese 832 is a red dwarf star with the stellar classification M1.5V, only 16.1 light years from the Sun. The star has an apparent visual magnitude of 8.66. It has about half the radius and mass of the Sun. A planet similar to Jupiter was found in the star’s orbit in 2002.
DEEP SKY OBJECTS IN GRUSNGC 7424
NGC 7424 is a barred spiral galaxy with an apparent magnitude of 11.0. It is approximately 37.5 million light years distant. The galaxy is about 100,000 light years in diameter and has well defined spiral arms, so it is called a “grand design” galaxy. So far, two ultraluminous X-ray sources and one supernova have been observed in NGC 7424.
The supernova SN 2001ig was classified as a Type IIb supernova, one that initially shows a weak hydrogen line in its spectrum, like typical Type II supernovas, but later the H emission becomes undetectable and is replaced by lines of oxygen, magnesium and calcium and there is a second peak in the light curve. Subsequently the supernova’s spectrum resembles a Type Ib supernova.
The supernova was discovered on the outer edge of the galaxy in 2001 by the Australian amateur astronomer Robert Evans. In 2002, Cambridge physicists discovered a binary companion to SN 2001ig, a massive star of the spectral type O or B with an eccentric orbit around the supernova progenitor star, which was believed to have been a Wolf Rayet star.
NGC 7424 is suspected to be a field galaxy, which is to say, while it is listed as a member of the IC 1459 Grus Group of galaxies, it is not gravitationally bound to any galaxy group.NGC 7213
NGC 7213 is a face-on, type 1.5 Seyfert galaxy in the constellation Grus.
It lies about 16′ to the southeast of the bright star Alpha Gruis.
It is one of the brightest spiral galaxies in Grus.
The galaxy is approximately 22 Mpc (71.7 million light years) distant from the Sun.
NGC 7140 is another spiral galaxy in Grus. It was discovered by the British astronomer John Herschel at the Cape of Good Hope in October 1834.
The galaxy has a visual magnitude of 11.7 and is approximately 37.4 Mpc (122 million light years) distant from Earth.
IC 1459 is a large peculiar elliptical galaxy in Grus. It has a fast counterrotating stellar core, shells and ripples.
The galaxy has an apparent visual magnitude of 10.97 and is 68.8 million light years (21.1. Mpc) distant.
IC 5264 is a spiral galaxy with a visual magnitude of 12, approximately 155.7 million light years (47.7 Mpc) distant from the Sun. It was discovered by the American astronomer Lewis Swift in June 1896.NGC 7418
NGC 7418 is a barred spiral galaxy in Grus constellation.
It was discovered by John Herschel on August 30, 1834.
The galaxy has an apparent visual magnitude of 10.9.
NGC 7421 is another barred spiral galaxy in Grus, also discovered by John Herschel in August 1834.
It has an apparent visual magnitude of 11.7.