Corvus belongs to one of the 48 original constellations of Ptolemy, and has endured to become one of the 88 modern constellations recognized by the International Astronomical Union. This small, box-like asterism has no bright star and consists of 11 stars which are visible to the unaided eye, yet Ptolemy only listed 7! There are 4 main stars and 10 which have Bayer/Flamsteed designations. Corvus is bordered by the constellations of Virgo, Crater and Hydra. It is visible at latitudes between +60° and ?90° and is best seen at culmination during the month of May.
In mythology, Corvus represents the Crow… and a charming tale at that. Legend tells us that the constellation of Crater is the cup of the gods. A cup befitting the god of the skies… Apollo. And who holds this cup, dressed in black? The Raven… Corvus. The tale is a sad one. The story of a creature sent to fetch water for his master, only to tarry too long waiting on a fig to ripen. When he realized his mistake, the sorry Raven returned to Apollo with his cup and brought along the serpent Hydra in his claws as well. Angry, Apollo tossed them into the sky for all eternity. It there they stay until this day…
For unaided eye observers, the Delta, Gamma, Epsilon and Beta (what appears to look like a figure 8, Y, E and B on the map) form an asterism that looks like a “sail”, and when connected seem to point to the bright star Spica. In Indian astronomy, the first five stars in Corvus correspond to the Hast nakshatra – a lunar zodiacal constellation. This is one of is one of the 27 or 28 divisions of the sky, identified by the prominent stars in them, that the Moon passes through during its monthly cycle. While it is Hindu, it is still very similiar to the divisions of the ecliptic plane referred to as the zodiac. The Moon takes approximately one day to pass through each nakshatra.
Let’s start with binoculars and down in the southern corner with Alpha Corvi – Alchiba. Alchiba belongs to the spectral class F0 and has apparent magnitude +4.00. It is 48 light years from Earth. This star is suspected of being a spectroscopic binary, although this has not yet been confirmed. Now take a look at Beta Corvi – Kraz. Good old Kraz is approximately 140 light-years away and is a G-type bright giant star whose apparent visual magnitude which varies between 2.60 and 2.66. Head west and look at Epsilon. Although it doesn’t look any further away, spectral class K2 III – Minkar – is 303 light years from Earth! Need a smile? Then take a look at Gamma. It’s name is Gienah and it literally means the “wing of the crow”. How about Delta? Algorab is a spectral class A0 and is about 87 light years from our solar system.
Now get out your telescope as we explore planetary nebula, NGC 4361 (RA 12 24 5 Dec -18 48). At around magnitude 10, this greenish disc is fairly easily spotted with smaller telescopes, but the 13th stellar magnitude central star requires larger aperture to be seen. It has a very symmetrical shape that is similar to a spiral galaxy. According to work done by Vázquez (et al): “The morphology of this object is complex given the highly filamentary structure of the envelope, which is confirmed to possess a low mass. The halo has a high expansion velocity that yields incompatible kinematic and evolutionary ages, unless previous acceleration of the nebular expansion is considered. However, the most remarkable result from the present observations is the detection of a bipolar outflow in NGC 4361, which is unexpected in a PN with a Population II low-mass-core progenitor. It is shown that shocks resulting from the interaction of the bipolar outflow with the outer shell are able to provide an additional heating source in this nebula.”
For galaxy fans, have a look at interacting galaxy pair, NGC 4038 and NGC 4039 – the “Ringtail Galaxy” (RA 12 01 53 Dec -18 52-3). This peculiar galaxy (also referred to as the “Antennae Galaxies”) were both discovered by Friedrich Wilhelm Herschel in 1785. Even in relatively small telescopes, you can see two long tails of stars, gas and dust thrown out of the galaxies as a result of the collision resemble the antennae of an insect. Most galaxies probably undergo at least one significant collision in their lifetimes. This is likely the future of our Milky Way when it collides with the Andromeda Galaxy. Two supernovae have been discovered in the galaxy: SN 2004GT and SN 2007sr. A recent study finds that these interacting galaxies are closer to the Milky Way than previously thought – at 45 million light-years instead of 65 million light-years. Geez… What’s 20 million light years between friends?