Corvus is a small constellation in the Southern Celestial Hemisphere. Its name comes from the Latin word ‘raven’ or ‘crow.’ Covering 183 square degrees and hence 0.446% of the sky, Corvus ranks 70th of the 88 constellations in area. It is bordered by Virgo to the north and east, Hydra to the south, and Crater to the west. In the equatorial coordinate system, the right ascension coordinates of the constellation 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.
Corvus and Crater, two adjacent constellations on the back of Hydra, shown on Chart XIX of the Uranographia of Johann Bode (1801). In ancient Greece, a krater was a bowl or vase used for mixing wine with water, rather than a cup as we know it. Johannes Hevelius’ Corvus from Uranographia (1690).
[http://www.ianridpath.com/startales/corvusandcrater.htm]
The constellation Corvus is named for the crow, a bird associated with Apollo. The star pattern looks nothing like a bird. It consists of four bright stars that form a quadrilateral and better fits the Arab designation of a tent, or the sailor’s lore that identifies it as a sail. This constellation was not created because it looked like a crow, but because it was near the constellation Hydra. While Hydra is chiefly associated with a very different story, the snake shape also reminded sky watchers of a fable about Apollo, written down by Ovid, which involved a crow, a water-snake and a cup. With one element of the story already in place (the snake), the two constellations, Corvus (crow) and Crater (cup) were created to represent the other two story elements. In ancient times, when stories were passed on by oral tradition, it was useful to have the main points of a fable hanging in the sky for all to see.
In the story, Apollo needed water to prepare a libation. He sent the crow, who did odd jobs for him, to bring water back in a cup. The crow was not known for having a serious or respectful attitude. At the water source, he found a tree of ripe figs and could not pass up feasting on them. He realized that he had kept Apollo waiting and that the god would be angry so he snatched up a water snake (not the infamous Hydra) and brought it back with him to blame for his delay. Apollo did not believe him and threw the crow, the snake, and the cup up into the sky. As a punishment, the crow is never able to reach the water in the cup. The crow and the raven (a related bird) were also associated with other stories about Apollo.
[http://chandra.harvard.edu/photo/constellations/corvus.html]
The Greek figure of Corvus is modeled on the Babylonian Raven (MUL.UGA.MUSHEN), which was similarly placed sitting on the tail of the Serpent (Greek Hydra). The Babylonian constellation was sacred to Adad, the god of rain and storm; in the second Millennium it would have risen just before the start of the autumnal rainy season.
In Chinese astronomy, the stars of Corvus are located within the Vermillion Bird of the South (Nán Fāng Zhū Què). The four main stars depict a chariot, Zhen, while Alpha and Eta mark the linchpins for the wheels, and Zeta is Changsha, a coffin.
In Indian astronomy, the first five stars of Corvus correspond to the Hastā, the 11th nakshatra or lunar mansion.
Corvus was recognized as a constellation by several Polynesian cultures. In the Marquesas Islands, it was called Mee; in Pukapuka, it was called Te Manu, and in the Society Islands, it was called Metua-ai-papa.
[http://www.go-astronomy.com/constellations.php?Name=Corvus]
Constellation of Corvus
[http://www.davidmalin.com/fujii/source/Crv.html]
Corvus includes only 11 stars with brighter than 4.02 magnitudes. 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 an asterism known as ‘the Spica’s Spanker’ or ‘the Sail.’ Gamma and Delta serve as pointers toward Spica.
Also called Gienah, Gamma Corvi is the brightest star in Corvus at magnitude 2.59. Its traditional name means ‘wing,’ the star marking the left wing. 154 light-years from Earth, it is a blue-white hued giant star 4.2 times as massive as the Sun. Around 160 million years old, it has 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 that is about 0.8 times as massive as the Sun. Around 50 AU 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. 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 (Algorab) means ‘the raven.’ It is one of two stars marking the right wing.
Marking the raven’s breast is Beta Corvi, a star of magnitude 2.7 located 146 light-years from Earth. Roughly 206 million years old and 3.7 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 light-years from Earth. It is a red giant that is around 54 times the Sun’s radius and 930 times its luminosity. Around 4 times as massive as the Sun, it spent much of its life as a main sequence star of spectral type B5V.
Also called Alchiba, Alpha Corvi is a white-hued star of magnitude 4.0, 48.7 light-years from Earth. It exhibits periodic changes in its spectrum over a three-day period, which suggests it is either a spectroscopic binary or (more likely) a pulsating Gamma Doradus-type variable. If the latter is the case, it is estimated to be 1.39 times as massive as the Sun. According to Bayer’s atlas, it lies above the bird’s beak.
R Corvi is a Mira variable star in the constellation Corvus, which ranges from a magnitude of 6.7 to 14.4 with a period of approximately 317 days. In the sky it appears close to Gamma Corvi and can be seen in the same binocular field. Extrapolating its luminosity from its period of 317 days yields a distance of 810 parsecs.
[https://en.wikipedia.org/wiki/R_Corvi]
VV Corvi is a close spectroscopic binary in the constellation Corvus. It is also an eclipsing binary, varying from magnitude 5.19 to 5.34 over 3.145 days. The two stars orbit each other with a period of 1.46 days and an eccentricity of 0.088. The mass ratio of the two stars is 0.775. The primary is about 2 times as massive as the Sun, 18 times its luminosity and has 3 times the Sun’s radius. The secondary is 1.5 times as massive as the Sun, about 5 times its luminosity and has 1.7 times the Sun's radius. Both are yellow-white main sequence stars of spectral type F5V, though the primary has begun expanding and cooling as it nears the end of its time on the main sequence. A tertiary companion was discovered during the Two Micron All-Sky Survey.
[https://en.wikipedia.org/wiki/VV_Corvi]
Two star systems have confirmed planets. HD 103774 is a young yellow-white main-sequence star of apparent magnitude 7.12 that is about 180 light-years distant from Earth. It is 1.3 times as massive and 3.5 times as luminous as the Sun. Variations in its radial velocity showed it was being orbited by a Neptune-sized planet every 5.9 days in 2013.
HD 104067 is an orange dwarf of spectral type K2V of apparent magnitude 7.93 that is about 70 light-years distant from Earth. Around 80% as massive as the Sun, it is orbited by a planet 3.6 times the mass of Neptune every 55.8 days.
A third star system, HD 111031 (50 G. Corvi), has an unconfirmed planet. HD 111031 is a class G5 star located 98 light years from Earth. HD 111031 b is a gas giant of around 3 Jupiter masses that orbits its star HD 111031 about every 6 days.
[https://en.wikipedia.org/wiki/HD_111031]
[https://en.wikipedia.org/wiki/HD_111031_b]
The center 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 center gives away its true nature:
Planetary Nebula NGC 4361
This infrared picture shows a dying star called NGC 4361. This star was once a lot like our sun, before it evolved and puffed out its outer layers. The object, called a planetary nebula, is unusual in that is has four lobes, or jets, of ejected material instead of the standard two. Astronomers suspect there might be two dying stars inside the nebula, each producing a bipolar jet. Orange primarily shows heated gas.
This image is one of the first to be taken during Spitzer’s warm mission- a new phase that began after the telescope, which operated for more than five-and-a-half years, ran out of liquid coolant. The picture was snapped with the two infrared channels that still work at Spitzer’s still-quite-chilly temperature of 30 Kelvin (about minus 406 Fahrenheit). The two infrared channels are part of Spitzer’s infrared array camera: 3.6-micron light is blue and 4.5-micron light is orange. This picture was taken while the telescope was being re-commissioned, on July 18.
[http://www.spitzer.caltech.edu/images/2710-ssc2009-15a3-Planetary-Nebula-NGC-4361]
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 ultraluminous x-ray sources, the source of which is unknown. Astronomers theorize that they may be a rare type of x-ray emitting binary stars or intermediate-mass black holes. The Antennae galaxies appear in a telescope at the 10th magnitude:
The Antennae
Some 60 million light-years away in the southerly constellation Corvus, two large galaxies collided. But the stars in the two galaxies cataloged as NGC 4038 and NGC 4039 don’t collide in the course of the ponderous, billion year or so long event. Instead, their large clouds of molecular gas and dust do, triggering furious episodes of star formation near the center of the cosmic wreckage. Spanning about 500 thousand light-years, this stunning view also reveals new star clusters and matter flung far from the scene of the accident by gravitational tidal forces. Of course, the visual appearance of the far-flung arcing structures gives the galaxy pair its popular name- The Antennae.
[http://apod.nasa.gov/apod/ap100507.html]
NGC 4027 is another member of the group, notable for its extended spiral arm, probably due to a past collision. Known as the Ringtail Galaxy, it lies close to 31 Crateris:
Arp 22 Stretches Out
NGC 4027, also known as Arp 22, stretches its single extended spiral arm in this face-on image. Located about 75 million light-years away in the constellation of Corvus (the Crow), this barred spiral galaxy is identified as a peculiar galaxy by this extended arm, thought to be the result of a collision with another galaxy millions of years ago- most likely a small galaxy known as NGC 4027A. NGC 4027 is part of the NGC 4038 Group, a group of galaxies that also contains the famous distorted couple known as the Antennae Galaxies.
This image is based on data collected with the ESO Faint Object Spectrograph and Camera (EFOSC) attached to the 3.58-metre New Technology Telescope (NTT) at the ESO La Silla Observatory in Chile. The data were collected through three broadband filters (B, V and R) and two narrowband filters (Hα and doubly ionized oxygen).
[https://www.eso.org/public/images/potw1030a/]
The Corvids (COR) were only seen by Cuno Hoffmeister, who noticed many slow meteors on several days around June 26, 1937, while observing from the southern hemisphere.
[http://cams.seti.org/maps.html]
Corvus hosts two established meteor showers. Cuno Hoffmeister discovered the Corvids in June 1937. In January 2013, the MO Video Meteor Network published the discovery of the Eta Corvids, their existence later confirmed by data analysis.
[https://en.wikipedia.org/wiki/Corvus_(constellation)]
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