Incredibly as we near the close of yet another year, a year that has already been rich in celestial sights for the sky-watcher, perhaps the climax of all-things-cosmic from the Earthlings’ point of view is about to commence with our Solar System’s brand new comet, ISON…
“Release the Kraken!” –oops, no: “Release the Cetus!” While many of us may recognise the former command as the correct one given by ‘Zeus’ in Louis Leterrier’s Clash of The Titans movie, we may just as easily have missed the fact that he actually named the ‘wrong monster’. While the Kraken, (essentially meaning ‘twisted’ or ‘crooked’ beast, hence the tentacles) is found in Scandanavian mythology, the classic portion of the tale upon which the recent film release is based or from which its characters originate, is Greek. According to the Greek myth the formidable beast to emerge from the deep is referred to as ‘Cetus’, so we can clearly infer that a little artistic license was taken in retelling the myth on the big screen! That branch of marine science known as ‘Cetology’ (the study of whales, dolphins, and porpoises) also takes its name from the Latin word “cetus” and farther back, the ancient Greek word “ketos”, both of which mean any ‘large sea animal’ or even ‘sea monster’. So with a constellation in the night sky named no less than ‘Cetus the Sea Monster’, for the stargazers among us who enjoy a good seafaring yarn you need look no farther than the heavens for entertainment!
While occasionally having been referred to as a “dragon”, in most versions of the classic myth Cetus was described as a “huge monster of the deep”, a “leviathan”, having a back “covered with barnacles” and a body “ending in a fish’s tail”. Although sometimes instead called ‘Cetus the whale’, as very few of those recorded species of sea mammals could be considered to have man-eating appetites and Poseidon’s retribution against the royal family of Argos was in sending Cetus to ‘devour’ Princess Andromeda, we can see why the alternative label of ‘sea monster’ stuck. So commencing our trip amongst the stars we’ll find the constellation of Cetus in the south (a little right of where the Sun rises in the morning). Although the celestial monster will be dead centre in this patch of sky 10pm mid-month we can ensure we’ve found the fourth largest star pattern by checking its position against the Great Square. High in the SW we can see our celestial quadrilateral and diagonally down to the left of it, Pisces the fish.
As we continue to move down to the horizon through this star pattern the fork from which the trail of stars ribbons out behind both fish points you to an interesting star in our sought-after constellation, Mira in the constellation of Cetus. Meaning ‘the wonderful’ this star is one of the finest examples of long period pulsating variable stars contained in this constellation. In effect magically ‘appearing’ and ‘disappearing’ for the naked eye observer approximately every eleven months, the red supergiant star 400 times the diameter of our Sun achieves this illusion by alternating its apparent magnitude from a bright 2.0 ‘down to’ a very dim 10. As a star in the last phases of its existence its physical expansion and contraction along with fluctuating temperature produces the variation in brightness. From this point rising toward the east is a large ring of stars representing the beast’s great head and containing the pattern’s second brightest star, Menkar. Often a disproportionately small body beneath sprouts one or two forelimbs or flippers, while the monster’s tail is marked with the pattern’s brightest star, Diphda, a class K1 2.0 magnitude star in the SSW.
Also contained within Cetus’s celestial territory is a rather magnificent gem, four large spiral galaxies in unusually close consort with one another within space, hence the object’s name, the ‘compact group’.
While the pleasurably darker evenings for sky-watching come hand-in-hand for those of us in the northern hemisphere with colder nights as well, let’s try and warm ourselves just a little in the west as we briefly return to that still beautiful asterism in the autumn night sky, the ‘Summer Triangle’. Having previously explored the distinctive avian theme spanning this great star pattern, it’s now time for us to join up the ‘final dot’ as we look up in the top left corner of the isosceles to the bright star Deneb, also a member of the constellation Cygnus the swan. Cygnus is the largest of the constellations of the triangle, whose birds were often associated with the deadly birds of Lake Stymphalos in the sixth ‘labour’ of Hercules. Despite their sharp-as metal beaks and claws the great Greek hero single-handedly exterminated them from the vicinity with the aid of a rattle and some handy Hydra poison-tipped arrows.
While ‘Cycnus’ (note the similarity of name), son of Aries and who after death was transformed into a swan is occasionally associated with this constellation, one of the main mythical explanations concerning the star pattern is that it represents the shape-shifting stunt Zeus once again pulled to successfully pursue Leda or Nemesis, and whose form he then placed in the heavens as a symbol of his triumph.
We’ve heard lots about it and many stargazers have already been viewing it and some even photographing it, so what makes November a special month in regards to Comet ISON? Well the answer is that this month hosts the comet’s ‘perihelion’ or its closest approach to the Sun. Yet despite this fact certainly sounding interesting, those of us who may consider ourselves less astronomically minded than the rest may still be wondering why this is significant. The simple answer is that unlike a meteoroid (a meteorite still in flight) which will clearly announce its presence by burning up and emitting light on its way through Earth’s atmosphere, just like a satellite a comet can only easily be seen with the naked eye in the darkness of space when it passes close enough to a light source, reflecting a sufficient amount of light toward the eye of the sky-watcher to be seen. This of course is exactly what will happen when our favourite 3-mile-diameter dirty snowball will pass by closest to the Sun on 28November while continuing its cross-sectional journey through the Solar System.
So just a few reminders as we prepare our eyes for the skies: Comet ISON will be rising in the East and is best seen not in the evening but in the early hours of the morning before the Sun rises; this month C/2012 S1 will glide past the constellation of Virgo’s bright star Spica and the planet Saturn; as it moves nearer the Sun it is getting brighter, was only magnitude 18 on the 1st October, far too dim to be seen without an optical aid, and for the majority of us needs to reach at least magnitude 4 to become visible to the naked eye; provided that it survives the traumatic gravitational pull and heat of the Sun (an estimated iron-melting 2700 degrees Celsius) our trajectory-labelled ‘Sungrazer’s’ maximum amount of melting ought to occur on the 28th extending its hopefully easily-spotted ball (or comet nucleus which may become as bright as Venus) with a majestic tail of vaporised ice streaking behind it across the dark sky. So if Comet ISON really does deliver any of the above, what more could we ask for?!
So as you look above to observe the great sights of the night sky in November, happy hunting and enjoy your interstellar voyage!
(Article by Nick Parke, Education Support Officer)