The Corvus Constellation

Corvus is a small constellation in the Southern Celestial Hemisphere. Its name means “raven” in Latin. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it depicts a raven, a bird associated with stories about the god Apollo, perched on the back of Hydra, the water snake. Covering 184 square degrees and hence 0.446% of the sky, Corvus ranks 70th of the 88 constellations in the area. It is bordered by Virgo to the north and east, Hydra to the south, and Crater to the west. The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of six segments. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 11h 56m 22s and 12h 56m 40s, while the declination coordinates are between −11.68° and −25.20°.Its position in the Southern Celestial Hemisphere means that the whole constellation is visible to observers south of 65°N.

The German cartographer Johann Bayer used the Greek letters Alpha through Eta to label the most prominent stars in the constellation. John Flamsteed gave nine stars Flamsteed designations, while one star he designated in the neighbouring constellation Crater—31 Crateris—lay within Corvus once the constellation boundaries were established in 1930. Within the constellation’s borders, there are 29 stars brighter than or equal to apparent magnitude 6.5. Four principal stars, Delta, Gamma, Epsilon, and Beta Corvi, form a quadrilateral asterism known as “the “Spica’s Spanker” or “the Sail.” Gamma and Delta serve as pointers to Spica. Also called Gienah, Gamma is the brightest star in Corvus at magnitude 2.59. Its traditional name means “wing”, the star marking the left wing in Bayer’s Uranometria. 154±1 light-years from Earth, it is a blue-white hued giant star of spectral type B8III that is 4.2+0.4-0.3 times as massive, and 355 times as luminous as the Sun. Around 160+40-30 million years old,  it has largely exhausted its core hydrogen and begun expanding and cooling as it moves away from the main sequence. A binary star, it has a companion orange or red dwarf star of spectral type K5V to M5V that is about 0.8 times as massive as the Sun. Around 50 astronomical units distant from Gamma Corvi A, it is estimated to complete an orbit in 158 years. Delta Corvi, traditionally called Algorab, is a double star divisible in small amateur telescopes. The primary is a blue-white star of magnitude 2.9, around 87 light-years from Earth. An enigmatic star around 2.7 times as massive as the Sun, it is more luminous (65–70 times that of the Sun) than it should be for its surface temperature of 10,400 K, and hence is either a 3.2 million-year-old very young pre-main sequence star that has not settled down to a stable main sequence life stage, or a 260-million-year-old star that has begun to exhaust its core hydrogen and expand, cool and shine more brightly as it moves away from the main sequence. Its spectral type is given as A0IV, corresponding with the latter scenario. Warm circumstellar dust—by definition part of its inner stellar system—has been detected around Delta Corvi A. Delta Corvi B is an orange dwarf star of magnitude 8.51 and spectral class K, also surrounded by circumstellar dust. A post-T-Tauri star, it is at least 650 AU distant from its brighter companion and takes at least 9400 years to complete an orbit. Delta Corvi’s common name means “the raven”. It is one of two stars marking the right wing. Located 4.5 degrees northeast of Delta Corvi is Struve 1669, a binary star that is divisible into two stars 5.4″ apart, 280 light-years from Earth. The pair, both white stars, is visible to the naked eye at magnitude 5.2; the primary is of magnitude 5.9, and the secondary is of magnitude 6.0

The raven’s breast is marked by Beta Corvi, a star of magnitude 2.7 located 146 ± one light-years from Earth. Roughly 206 million years old and 3.7 ± one times as massive as the Sun, it has exhausted its core hydrogen and expanded and cooled to a surface temperature of around 5,100 K and is now a yellow, bright giant star of spectral type G5II. It likely spent most of its existence as a blue-white main sequence star of spectral type B7V. Bearing the proper name of Minkar and marking the raven’s nostril is Epsilon Corvi, located some 318 ± five light-years from Earth. It is a red giant of spectral type K2III that is around 54 times the Sun’s radius and 930 times its luminosity. Around four times as massive as the Sun, it spent much of its life as a main-sequence star of spectral type B5V. Lying to the south of the quadrilateral between Beta and Epsilon Corvi is the orange-hued 6 Corvi, an ageing giant star of spectral type K1III that is around 70 times as luminous as the Sun. It is 331 ± ten light-years away from Earth.

Corvus contains no Messier objects. It has several galaxies and a planetary nebula. The centre of Corvus is home to a planetary nebula, NGC 4361. The nebula itself resembles a small elliptical galaxy and has a magnitude of 10.3, but the magnitude 13 star at its centre gives away its true nature.  The NGC 4038 Group is a group of galaxies across Corvus and Crater. The group may contain between 13 and 27 galaxies. The best-known member is the Antennae peculiar galaxy, located 0.25 north of 31 Crateris. It consists of two interacting galaxies—NGC 4038 and 4039—that appear to have a heart shape as seen from Earth. The name originates from the huge tidal tails that come off the ends of the two galaxies, formed because of the spiral galaxies’ original rotation. Both original galaxies were spiral galaxies and are now experiencing extensive star formation due to the interaction of gas clouds. The galaxies are 45 million light-years from Earth, and each has multiple ultra-luminous X-ray sources, the source of which is unknown. Astronomers theorise that they may be a rare type of x-ray emitting binary stars or intermediate-mass black holes. The Antennae Galaxies appear at the 10th magnitude. SN 2004gt was a type Ic supernova that erupted on December 12, 2004. The progenitor was not identified from older images of the galaxy and is either a type WC Wolf–Rayet star with a mass over 40 times that of the Sun, or a star 20 to 40 times as massive as the Sun in a binary star system. SN 2007sr was a Type Ia supernova event that peaked in brightness on December 14, 2007. NGC 4027 is another member of the NGC 4038 group, notable for its extended spiral arm. Known as the Ringtail Galaxy, it lies close to 31 Crateris. A barred spiral galaxy, its distorted shape is probably due to a past collision, possibly with the nearby NGC 4027A. NGC 4782 and NGC 4783 are a pair of merging elliptical galaxies in the northeastern part of the constellation, around 200 million light-years distant.

Two established meteor showers originate from within Corvus’ boundaries. German astronomer Cuno Hoffmeister discovered and named the Corvids in 1937, after observing them between June 25 and July 2. They have not been seen since, nor was there evidence of a shower when previous records were examined. In January 2013, the MO Video Meteor Network published the discovery of the Eta Corvids, assigning some 300 meteors seen between January 20 and 26. Their existence was confirmed by data analysis later that year. Credit: Wikipedia.