Corvus (constellation)

Corvus (Latin for raven) is a minor constellation with only 11 stars visible to the naked eye. γ Corvi (Gienah Gurab) and δ Corvi (Algorab), serve as indicators to find Espiga (α Virginis).

Notable features

Constellation of the Raven

Corvus's brightest star, γ Corvi, is officially named Gienah. It is a bluish-white giant of spectral type B8III with an anomalous chemical composition; it presents high levels of mercury and manganese, as well as unusually low levels of aluminum and nickel, being included within the group of mercury-manganese stars.

Next in brightness is β Corvi, named Kraz, a luminous yellow giant of spectral type G5II, 192 times more luminous than the Sun, located 146 light-years from the solar system. Algorab (δ Corvi)—the third brightest star in Corvus—is a binary whose main component is a subgiant of type A0IV accompanied by an orange dwarf. ε Corvi is an orange giant with an effective temperature of 4260 K, 740 times more luminous than the Sun. For its part, Alchiba, the name given to α Corvi, is a main sequence star of type F1V distant 49 light years from the solar system.

Another star of interest is η Corvi, a F2V type star where an excess of infrared radiation has been detected, indicating the existence of a circumstellar disk. Most of the inner 100 AU of the disk is relatively clear of material, suggesting that it may have been cleared by a planetary system. Similar but somewhat cooler, HD 103774 is a star with a planet whose mass is comparable to that of Saturn. Around HD 104067, an orange dwarf of type K3V, an extrasolar planet has also been discovered. HD 111031, 101 light-years distant, is a yellow dwarf cooler than the Sun with a brown dwarf companion.

Among the variables of the constellation, VV Corvi deserves attention, a complex stellar system composed, in the first instance, of two F3IV type subgiants. In turn, both stars are spectroscopic binaries and one of them is also an eclipsing binary with an orbital period of 1,460 days. Another variable, TV Corvi—known as Tombaugh's Star—is a dwarf nova that was serendipitously discovered as a 12th magnitude star in a 1932 plate by Clyde Tombaugh while searching for trans-Neptunian planets. Its identity as a dwarf nova was confirmed by David Levy in 1990.

Infrared image of planetary nebula NGC 4361

Among the objects of deep sky are NGC 4038 and 4039, two galaxies interacting, known as Antennae Galaxys. They are experiencing galactic collision and the nuclei of both galaxies are joining to form a supergalaxia, probably elliptical type. Both are members of the NGC 4038 Group.

NGC 4361 is also found in Corvus. At a distance of about 1.3 kiloparsecs, it is a multilayered planetary nebula whose chemical abundance and distance to the galactic plane correspond to a Population II object.

Main Stars

• α Corvi (Alchiba), with magntitude 4,02 is only the brightest fifth of the constellation despite its denomination Alpha. According to Bayer's atlas, it lies above the bird's beak.
• β Corvi (Kraz), the second brightest with magnitude 2,65, a giant yellow star.
• γ Corvi (Gienah Gurab or Gienah Corvi), the brightest with magnitude 2,58, a white-suclided star. It belongs to the group of mercury-manganese stars and is 165 light years away.
• δ Corvi (Algorab), of magnitude 2,94 is an easy to observe double star. The weakest component is a very young star, with only 110 million years old.
• ε Corvi (Minkar), giant orange star of magnitude 3.02.
• γ Corvi, star Be of magnitude 5,20; forms a double optic with another star at 11.2 seconds of arc.
• MIL Corvi, star of magnitude 4,31 with a circum-stellar disc around similar to that of Vega (α Lyrae).
• 3 Corvi, white star of magnitude 5.46.
• R Corvi, variable star Mira, whose brightness ranges between magnitude 6.7 and 14.4 in a period of about ten months.
• TU Corvi, Delta Scuti variable whose period is 1.97 hours.
• TY Corvi (31 Crateris), rotating ellipsoidal variable of mean magnitude 5.26.
• TZ Corvi, star of galactic halo with very low metal content.
• VV Corvi, eclipsing star system of average magnitude 5.27.
• HD 111031, yellow dwarf accompanied by a brown dwarf.
• HD 111980, halo star very low metallic.
• WD 1202-232, distant white dwarf 35 light years.

Deep Sky Objects

Image of Antennae Galaxys obtained by Hubble Space Telescope

• NGC 4027, a coiled spiral galaxy with a large arm than the rest.
• NGC 4038 and NGC 4039, two galaxies in interaction known as Antennae Galaxys. Located west of the constellation, 4th southeast of Gienah Gurab (γ Corvi).
• NGC 4361, planetary nebula of a light blue color.

Meteor rains

Two established meteor showers originate within the boundaries of Corvus. The German astronomer Cuno Hoffmeister discovered and named 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. Hoffmeister noted that the shower's trajectory was similar to that of comet 11P/Tempel-Swift-LINEAR, although this was not confirmed by Zhukov and colleagues in 2011. The shower has been tentatively linked to the asteroid (4015) Wilson-Harrington. In January 2013, the MO Video Meteor Network published the discovery of Eta Corvids, assigning some 300 meteors seen between January 20 and 26. Its existence was confirmed by data analysis that same year.

Mythology

In Greek mythology, a raven was a servant of Apollo, and he sent it with the cup (constellation of the Cup) to bring him water, but the raven was late in returning because it was waiting for a fig to ripen near the spring. He brought the cup and a water snake between his claws and told Apollo that he had been delayed because the snake had attacked him. Apollo, knowing that the raven was lying, put the three in heaven: he condemned the raven to be always thirsty, because although the cup is close, the serpent (Hydra constellation) does not allow him to drink.

Additional bibliography

• Ridpath, Ian; Tirion, Wil (2001). Stars and Planets Guide (in English). Princeton University Press. ISBN 0-691-08913-2.