Corvus is the 70th largest of the 88 constellations, and consists of 4 main stars which form a quadrangle in the night sky, the brightest of which is a blue-white giant of 2.59 magnitude called Gienah. The name Corvus means “crow” or “raven” in Latin, and it is associated with the nearby constellations of Crater (Cup), and Hydra (Water Snake).
This tiny constellation, which takes up an area of only 184 square degrees of the southern sky, can be seen by people located between latitudes +60° and -90°. From the northern hemisphere, Corvus can be seen during the winter and spring time, although it is best seen at around 9 PM (Local Time) during the month of May, while from the southern hemisphere, the constellation appears overhead from April to June. Look for the Crow perched on the back of Hydra, between Virgo and its bright star Spica to the northwest, and Crater almost due east. Four of the brightest stars in the constellation form a distinctive quadrilateral figure in the sky, which is not difficult to find.
The constellation is taken to represent the god Apollo’s once-sacred crow. While most mythological figures were placed in the sky as a sign of honour and respect, Corvus was placed in the sky as punishment for failing to fetch water for Apollo in a timely fashion. Instead, the crow dallied by a fig tree several days eating its fruit, and subsequently lied to Apollo by blaming the serpent Hydra for blocking the spring. Unconvinced by his lies, Apollo then flung the crow, the cup, and the water snake he brought in his claws into the heavens, while Corvus was also punished with eternal thirst, which it why crows have a rasping caw, unlike other birds which sing.
Although Corvus has no bright stars, its four brightest stars form a distinctive asterism known as THE SAIL (SPICA’S SPANKER), which is made up of Delta, Gamma, Epsilon, and Beta Corvi. The two stars Gamma and Delta Corvi serve as pointers to the star Spica, the most luminous star in Virgo, and the 15th most luminous star in the entire sky.
– Gienah (Gamma Corvi) is a binary system located 154 light years from the Sun that shines with a visual magnitude of 2.59, making it the most luminous star in the constellation. Its primary component is a giant blue star (B8 III-class) that is separated from its companion by around 50 AU. The name Gienah derives from the Arabic phrase for “the right wing of the crow.”
– Kraz (Beta Corvi), the constellation’s second most luminous star, is a G-type yellow giant star found about 140 light years away with an apparent visual magnitude of 2.65. Being a variable star, however, means that this figure can range from between 2.60, and 2.66. Although the star was named “Kraz” comparatively recently, nobody is quite sure who named it thus, or why. What is known about Kraz, though, is that it is around 206 million years old, and has 16 times the Sun’s radius, 3.7 times its mass, and is at least 160 times brighter.
– Algorab (Delta Corvi), the third most luminous star in Corvus, is a blue subgiant situated 87 light years from our solar system with an apparent magnitude of 2.96. It is around 2.7 times more massive than our sun, and 69 times brighter. Algorab derives from the Arabic word meaning ‘the crow’.
– Minkar (Epsilon Corvi), the constellation’s fourth brightest star, is a red giant (K2 III) located 318 light-years away of magnitude 3.02. It has around 52 times the Sun’s radius, and is 4 times more massive. Minkar derives from the Arabic phrase meaning “the nostril of the crow.”
Other stars of interest in Corvus includes the blue-white subgiant Alchiba (Alpha Corvi); the eclipsing binary star VV Corvi; and Eta Corvi, a F2 V-class main sequence dwarf with an apparent visual magnitude of 4.31. But what sets Eta Corvi apart from other stars in Corvus is that like the star Vega in Lyra, it is surrounded by a debris disc. Furthermore, recent research has revealed the presence of a second debris disc, which is unusual for a star of this size.
Even though the constellation has no Messier objects, it is home to the Antennae Galaxies, which is one of the most spectacular and famous galactic mergers yet discovered, as well as NGC 4361, a beautiful planetary nebulae .
– Antennae Galaxies (NGC 4038/NGC 4039, Caldwell 60/61) is a pair of colliding galaxies that has a combined apparent visual magnitude of 11.2 from a distance of about 45 million light years away. Also known as the Ring Tail, this merger is a member of the NGC 4083 Group, an assembly of galaxies with between 13 and 27 members that fall in both Corvus and the neighbouring constellation Crater. The galactic encounter is estimated to have started about 900 million years ago, and around 600 million years ago the galaxies actually collided and passed through each other, which caused both galaxies to begin ejecting stars around 300 million years ago.
During the past 300 million years the number of ejected stars had grown so large that collectively they appear as an extension of the pairing resembling the antennae of an insect, hence the name Antennae Galaxies. One such antenna can be seen as the blue, fuzzy area to the right of the curved, pink star forming region in the upper galaxy. It is estimated that the merger will be complete in about 400 million years’ time, when the pair will settle down into a large elliptical galaxy.
– NGC 4027 is a barred spiral galaxy found 83 million light-years from Earth with a visual magnitude of 11.7. It is remarkable in as much as one of the galaxy’s spiral arms stretches further out than other examples of its kind, possibly due to having collided with another galaxy in the past.
– NGC 4361 is arguably one of the most spectacular planetary nebulae discovered, as well as one of the largest. NGC 4361 spans an area of about 1.3 degrees, and unlike most planetary nebulae that have two lobes of ejected matter, this one has four distinct lobes, giving the nebula the appearance of a small irregular galaxy. It also has the 13th magnitude remains of a progenitor star in the centre of its bubble of gas and dust.
The only active meteor shower currently associated with the constellation is called the Eta Corvids, which was discovered in 2013 when 300 meteors were observed between January 20th and 26th. Another meteor shower, the Corvids, seems to have disappeared after its discovery in 1937 in what is now Namibia. In that year, the shower peaked on June 26th with a maximum rate of 13 meteors per hour. This shower has never been observed after 1937, though, and no trace of it has since been detected even with radio and radar surveys.
Ptolemy clearly drew heavily on the Babylonian crow constellation MUL.UGA.MUSHEN, which was depicted in Babylonian charts as a bird perching on the tail of a serpent of some sort. In Babylonian times, the constellation was linked to Adad, the deity of Rain and Storms, no doubt because in those times, the constellation rose just before the onset of the wet season.
As of 2016, the constellation has two stars with one planet each. Neither star is visible to the naked eye.