Friday, May 18, 2012

The constellation Corvus

This is an excellent time of year to view the constellation Corvus, the Raven (or the Crow).  Currently, he is high in the southern sky, transiting (reaching his highest point on his nightly arc, arcing upwards from the east prior to transit and then downwards towards the west after transit) at about 10:30 pm at latitude 35 North.  

Corvus is easy to locate if you can find Virgo the Virgin, and Virgo is also easy to locate after sunset in the hours before midnight this time of year.  She follows Leo the Lion quite closely (giving rise to the many ancient goddesses who either ride a lion or ride chariots pulled by a lion).

Currently, the planet Saturn is located in Virgo, very close to her brightest star, Spica (see the diagram in the post linked with the first link in the previous paragraph, which has a helpful red arrow pointing to Spica).  Saturn is yellowish in color and glows with a steady bright glow, unlike the twinkling stars (planets do not twinkle, just as the moon does not -- they are bodies in our solar system and reflect the sun's light as does the moon, but since they are farther away they appear to be similar in size to the stars).

Once you have found Virgo, you may well look around and wonder what that bright grouping of stars might be, close in the sky below her -- a fairly bright quadrilateral of stars glowing brightly in a relatively dark patch of sky beneath Spica (and Saturn) and off to the right (or west -- all descriptions here are northern-hemisphere-centric).  This is Corvus, and as you become familiar with his constellation, he will really begin to resemble a crow or a raven, sitting there with his bill pointed towards Virgo and his tail-feathers pointing downwards.

The diagram above shows the constellation Corvus, and the original image has the grey lines as his outline is typically drawn in many star-charts, but they are not very helpful.  Much better (as usual) is the outline (added in green lines above) suggested by H.A. Rey, the beloved author of children's books including the Curious George series, whose book The Stars: A New Way to See Them is a wonderful companion for anyone interested in becoming familiar with the constellations of our night sky.

On page 50, describing this constellation, he says of Corvus:
Small but quite bright, below the Virgin's head.  The star and the tip of the bill, and the one where the leg joins the bird's body, are rather faint, so the complete shape of the sitting crow can only be seen under best conditions, but the four brightest stars of the constellation, forming a quadrangle, are easily found.  The Crow's bill is pointed toward the Virgin's jewel, Spica, as though he were waiting for a chance to grab it.
This is a wonderful description, and quite apt for the bird, as you will see for yourself when you locate him.

Here is a link to the delightful "Constellation of Words" website discussion of Corvus and the ancient legends surrounding this constellation (which was known in the ancient world and described by Ptolemy in his Almagest).  Note the legends in which the Raven was charged with watching Coronis, a beautiful young princess and the daughter of King Phlegyas, while she was pregnant with his son, Asclepius.  

This is another example of evidence supporting the argument that the myths encode information about the heavenly bodies, rather than (as most people think) the other way around (the "other way around" would be the idea that the planets were named after the gods, when in fact the gods were named after the planets, or in some cases the constellations).  The myth of a raven watching a princess is almost certainly inspired by the constellation Corvus watching the Virgin.

Another important aspect of the constellation Corvus  is the appearance of a raven among the other animals depicted in the tauroctony scenes present in the mithraea of the ancient Roman mystery religion of Mithraism (also known to the ancients as the Persian Mysteries).  

Professor David Ulansey's Origins of the Mithraic Mysteries: Cosmology and Salvation in the Ancient World presented the case for interpreting the imagery of the tauroctony scene based upon constellations and other aspects of celestial mechanics.  This interpretation stands in marked contrast to the conventional view held by most academic scholars of Mithraism, who for nearly a hundred years had interpreted the various figures depicted in the tauroctony scene as representing the various types of creatures that sprang from a slain bull as part of a Zoroastrian creation legend.

Instead, Professor Ulansey argues that figures present in the tauroctony represent the constellations along the celestial equator as it was when the equinoxes were in Taurus and Scorpius, namely: "Taurus the bull, Canis Minor the dog, Hydra the snake, Crater the cup, Corvus the raven, Scorpius the scorpion" (51).  

He also gives some evidence which argues that the cup (when it appears in the tauroctony) may represent Aquarius rather than Crater, because the cup does not always appear in the tauroctony but when it does it usually does so with a lion, and thus the bull, scorpion, cup and lion could represent the four constellations that guarded the equinoxes and solstices during the epoch depicted (52).  However, this debate does not concern Corvus, as the image of a raven is a fixture in most of the tauroctonies, whether they also have an image of a lion and a cup or not.

An astute observer of the heavens as they are today, or of the star map above showing Corvus and identifying the celestial coordinates along the edge of the map, will notice that Corvus does not lie along the celestial equator, which would seem to argue against Professor Ulansey's theory.  However, the observer must also remember that due to the phenomenon of precession, the celestial equator (as well as the celestial north and south poles) moves against the background of stars.  

Just as the central point around which the sky appears to turn moves over the millenia until it is beneath different stars (currently almost precisely beneath Polaris, but thousands of years ago beneath Thuban in Draco instead), so the celestial equator shifts along with it, such that the line of the celestial equator passed through those constellations in a previous age but it no longer does so today.  Thousands of years ago, the celestial equator passed right through Corvus.

For all these reasons, becoming familiar with the small but important constellation Corvus is worth making the effort to do this time of year.