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Constellations: Corvus 'the Crow'

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The shield of the Science, Mathematics and Engineering faculty of the h2g2 University.Constellations: Overview | Andromeda | Antlia | Apus | Aquarius | Aquila | Ara | Aries | Auriga | Boötes | Caelum
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Beauty too rich for use,
For earth too dear!
So shows a snowy dove trooping with crows,
As yonder lady o'er her fellows shows.

–  William Shakespeare Romeo and Juliet Act I, scene V.

Name:Corvus (Latin: 'crow')
Genitive:Corvi
Short form:Crv
Area:184 sq deg
Co-ordinates1:12h, −20°
Origin:Ancient

Corvus is a small southern constellation which shares its borders with Virgo, Crater and Hydra. The outstanding attraction of this unremarkable collection of stars is what lies far beyond them: a merging pair of spirals known as The Antennae Galaxies. This stunning image at the Astronomy Picture of the Day website captures a strikingly romantic portrait of the entwined pair embracing.

History

Corvus began life as 'the raven', according to the ancient Greeks, and it featured in Ptolemy's original 48 constellations of the Almagest. In some cultures the smaller constellations Corvus, Crater 'the Cup' and Sextans 'the Sextant' were once the humps on the back of Hydra 'the Sea Serpent'.

A raven features in the Biblical story of Noah. After the deluge he released a raven, but it didn't leave, choosing instead to feed on the carcasses floating in the water, so the more reliable dove was sent next.

And he sent forth a Raven, and it went forth and to and fro, until the waters were dried up from off the Earth.
Genesis 8:7.

Julius Schiller

One pious astronomer, German cartographer Julius Schiller (1580 – 1627), published his Christian star atlas Coelum Stellatum Christianum in 1627, just before he died. Schiller basically redrew the ancient heavenly shapes (which he thought were Pagan in origin) as images of Biblical figures. The signs of the Zodiac were replaced by the 12 Apostles. Schiller grouped Corvus and neighbouring Crater together, creating a new constellation to represent the Ark of the Covenant.

Mythology

The main myth of Corvus concerns the Greek gods themselves. The god Typhon was a fearsome monster from whom all the other gods fled when he stormed Mount Olympus. Even the mighty Zeus, who had morphed into the form of a ram, could not escape and he was imprisoned by Typhon. The god Apollo turned himself into a crow or raven to escape. Typhon was eventually defeated when Zeus trapped him by dropping Mount Etna on him. Being immortal, the god Typhon could not die, so he remains trapped beneath the earth, erupting when disturbed. The disguised images of the fleeing gods were placed in the night sky as a reminder against complacency.

Another story also concerns Apollo. He commanded his pet crow (or raven) to fetch him some fresh water from Earth. The bird returned late because it had waited for some fruit to ripen. It then told its master a tall tale that it had been attacked by a water serpent, as its excuse. Apollo didn't believe the story and the furious god expelled it to the night sky above Earth, where it became the group of stars known as Corvus. The hapless serpent created the constellation Hydra, and the spilled goblet formed Crater 'the Cup'.

Stars

The scientific star names are quite simple to understand. Greek small case letters 'alpha', 'beta', etc, are combined with the genitive form of the constellation to give what is known as the 'Bayer designation'. Some stars have proper names as well, for example, alpha Corvi is Alchiba. Other stars are known by their catalogue number. Usually the alpha star is the brightest of the constellation, but sometimes errors were made at the time of cataloguing, or the stars were named by order. It's not known why the alpha designated star of Corvus was awarded to the fifth-brightest.

Gamma Corvi has the common name Gienah Ghurab which is Arabian meaning 'the bird's wing'. This blue-white giant is the luminary of the constellation at +2.6 magnitude.

Kraz (beta) is a yellow giant variable star just a fraction less bright than Gienah Ghurab.

Algorab (delta) is a binary system comprising a different coloured twosome.

Minkar (epsilon) is an orange giant variable.

Alchiba (alpha) is a white dwarf and a relative neighbour at just 48 light years2 distant.

Star Table

StarDesignationName or
catalogue number
Brightness (m)Distance
(light years)
Spectral classification
and/or comments
γ Crvgamma CorviGienah Ghurab+2.6165Blue-white giant
β Crvbeta CorviKraz+2.65 var140Yellow giant
δ Crvdelta CorviAlgorab+2.88 var88Binary
ε Crvepsilon CorviMinkar+3.03 var300Orange giant
α Crvalpha CorviAlchiba+4.02 var48White dwarf
η Crveta CorviAvis Satyra+4.360Yellow-white dwarf
ζ Crvzeta Corvi5 Corvi+5.2385Double star

Extrasolar Protoplanets

Avis Satyra (eta Corvi) is a yellow-white dwarf which has a protoplanetary disc at a distance of 180AU3. This means that the system may evolve planets but they will not be in the habitable zone.

New General Catalogue (NGC)

The NGC was compiled by John Louis Emil Dreyer (the director of the Armagh Observatory from 1882 - 1916).

NGC 4038 and NGC 4039 are collectively known as The Antennae Galaxies. The stately pair of spiral galaxies have so far spent 800 million years merging with each other. In an ultimate slow dance, they will eventually become one single unit.

NGC 4361 is a planetary nebula which features on the best of AOP website. It was discovered by Sir William Herschel (1738 - 1822).

NGC Table

CatalogueTypeBrightness (m)Distance
(light years)
Remarks
NGC 4038/9Galaxies+10.3/+10.690 millionMerging pair
NGC 4027Galaxy+1168 millionPost collision
NGC 4802Galaxy+1260 millionSpiral
NGC 4361Planetary nebula+11114,000Herschel 1.65

Meteor Shower

The space debris which creates a meteor shower comes from the tail of a comet, as the Earth crosses where the comet passed previously on its own orbit. Imagine a trail of breadcrumbs, or sawdust like that used in hashing.

The meteor showers connected with this constellation are called the Corvids. They appear between 25 June and 3 July, with the maximum being 27 or 28 June. They were first discovered in 1937 by C Hoffmeister whilst on an astronomical expedition to South Africa. The ZHR (Zenithal Hourly Rate) is less than ten; with only a minor activity rating, this isn't a shower for the diary.

Extrasolar Planets in Corvus

There are two extrasolar planetary systems in the constellation Corvus. The table below shows the length of the planet's orbital period around its parent star, which we know of as a year. The mass of the extrasolar planet is compared to that of Jupiter, our Solar System's largest planet, known by astronomers as the 'Jovian scale'.

Extrasolar Planets Table

Star name or
catalogue number
Planet
catalogue number
Planet mass
(Jovian scale)
Orbital period
(Earth days)
Year of discoveryComments
HD 111031HD 111031 b2.875,9862007Superjovian
HD 104067HD 104067 b0.1655.82009Hot gas giant

Down to Earth

Corvus in Nature

The family Corvidae includes large birds of black or dark plumage, stout beaks and a distinctive loud screechy call which sounds like 'caw'. Carrion crows, magpies, rooks, ravens and jackdaws all belong to this group. They can be attracted to shiny objects which they steal to decorate their nests. Ravens are arguably the most intelligent members of the bird kingdom. They devise clever bluffing strategies to put their rivals off the scent when they're caching food.

Roman Corvus

The corvus was a Roman invention which aided them in sea battles. Their foes the Carthaginians were superior sailors, so to restore the advantage the Romans built a bridge attachment to their own vessels which could be utilised for boarding enemy ships. The bridge was approximately 36ft in length and up to 4ft wide with a parapet running the full length along each side. The Roman ship would manoeuvre into position then winch out the corvus. The heavy-spiked extreme end would be dropped onto the opposing vessel's hull and the Roman soldiers would run across the gap thus enabling hand-to-hand combat, which was the Roman prowess.

Raven Legend

The 11th-century Tower of London on the River Thames is one of Europe's biggest tourist attractions. This is where the Crown Jewels belonging to the British monarch are kept. There is a legend involving ravens (Corvus corax), which have lived at the fortress for over three centuries. A prophecy dates back to the beginning of the reign of King Charles II, who ruled from 1660 to 1685. He decreed that at least six ravens should always be kept at the Tower4. The story foretells a terrible disaster that will befall the kingdom if the Tower of London ever loses its feathered residents. So seriously is the superstition taken that the birds have their own 'Ravenmaster', currently Derrick Coyle. Since the bird 'flu scare of 2005 the six 'guardians of the Tower': Baldrick, Branwen, Gwyllum, Hugine, Munin and Thor, are kept in an aviary indoors, their lodgings are next to the Wakefield Tower. Hugine and Munin are not just Tower ravens but Thought and Memory, the messengers of Wotan (Odin).

Corvidae in the Edited Guide

Prose by Poe

The Raven - a poem by Edgar Allan Poe. Nevermore.

And Finally

  • Crows are tricksters, according to Native American legends.

  • 'Eating crow' is an American term which means the same as 'eating humble pie' – a figure of speech meaning to apologise for making a mistake.

1Current IAU guidelines use a plus sign (+) for northern constellations and a minus sign (−) for southern ones.2A light year is the distance light travels in one year, roughly 5.88 trillion miles or 9.46 trillion km.3Astronomical Units. One AU is the mean distance from the Sun to the Earth, approximately 150 million km.4This was against the wishes of his Astronomer Royal John Flamsteed who declared the birds a menace because they interfered with his observations from the Royal Observatory in Greenwich.

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