OCTOBER 2013 SKYLIGHTS by Mark Dawson, Whitby & District Astronomical Society
|
Most of the planetary action occurs in the early morning sky this month, although by mid-October conspicuous Jupiter is visible low in the eastern sky by 11pm, residing below the ‘twins’ of Gemini. Jupiter is a fine sight through any telescope. The bright ‘banded’ disk and Galilean moons make it particularly appealing for anyone just getting started in astronomy. Our moon lies below Jupiter on the 26th. Red Mars follows a couple of hours behind Jupiter, though is not as bright. From the 10th to the 20th Mars passes just above Regulus, the chief star in the ‘sickle’ of Leo. Look on the 15th when comet ISON (which may become a brilliant object by late November) lies just above Mars; you will however require a telescope to spot it at this point in time.
The Moon joins Mars and Regulus on the 1st, 29th and 30th. Following the summer star party season the first autumn/winter monthly meeting of Whitby and District Astronomical Society will be held on Tuesday 1 October at Whitby Community College, main block, room H1 from 7.30 pm. If you are interested in joining our friendly society please come along. |
Signposts in the Night Sky
THE CELESTIAL OCEAN – ‘BEAR TALES, TIARAS AND THE WINGED SIGNPOST’ After reading numerous astronomy books, as a young boy of seven I was inspired by the many tales and legends associated with the constellations. I can still vividly recall the excitement of acquiring my first pair of binoculars, venturing out into the back garden and taking my first steps in what has become a lifelong hobby. I was keen to identify these stellar patterns for myself. It was early October, nights were drawing in rapidly and the heavens were a magical playground in which to explore. It is not surprising that I view the first few weeks of October with a certain amount of nostalgia! THE PLOUGH, THE GREAT BEAR, URSA MAJOR AND URSA MINOR I took my first celestial steps around one of the best-known star patterns, the Plough, the outline of which resembles a ‘dot to dot’ saucepan (also known as the Big Dipper). The Plough is really an asterism, a distinctive pattern within a constellation, in this case Ursa Major, the Great Bear. As it endlessly circles around the celestial pole, throughout autumn the Plough resides at an observer friendly altitude low in the NNW. In Greek mythology Ursa Major represents Callisto, daughter of King Lycaon of Arcadia who, after a liaison with Zeus bore a child, Arcas. In order to save Callisto from his enraged wife Hera, Zeus turned Callisto into a bear. Many years later whilst out hunting, Arcas was about to kill a large bear but knowing this was Callisto, Zeus hurriedly intervened and turned Arcas into a bear too. Reunited, mother and son were swung into the heavens by their tails, out of harm’s way. Ursa Minor represents Arcas. 
Five of the stars forming the Plough asterism are genuinely associated, sharing the same speed and trajectory through space. These, along with a number of others scattered around the sky including the brilliant winter star Sirius, are all members of the Ursa Major moving star cluster. Sometimes referred to as the ‘horse and rider’, anyone with half decent eyesight should be able to detect that the middle star in the Plough handle is double. Binoculars show Mizar and Alcor well, but a telescope also reveals that Mizar itself is a striking double star.
Numerous deep sky objects are dotted around Ursa Major, most of which require a telescope to spot, but the twin galaxies of M81 and M82 are somewhat brighter, visible as smudges of light in binoculars. The lesser bear of Ursa Minor is rather a faint constellation, but does contain Polaris – our current pole star. Use the ‘pointer’ stars to track it down. Return to the Plough and follow round the curve of the handle to locate Arcturus, the brilliant orange star low in the WNW in the constellation of Bootes, the Herdsman. To the upper left of Arcturus look for the delicate starry circlet of Corona Borealis – the Northern Crown. Its leading star, Gemma, is set in the midst of this pleasing arrangement. According to Greek legend Corona represents the crown of the wine god Dionysus, which he tossed into the heavens to prove his love for Ariadna. She had recently been deserted by Theseus (of the Minataur legend) vowing never to marry a mortal again. She did however wed Dionysus. The Herdsman’s dogs, Canes Venatici, are situated beneath the Plough handle and are marked by two stars. The brighter one, Cor Caroli, meaning Charles’s heart, was named in honour of King Charles I. However my favourite tale for this part of the sky stems from the Iroquois Indians and ties in Corona, Arcturus and the stars of the Plough. In this, a huge bear represented by the ‘bowl’ stars of the Plough is hunted by seven warriors. The three strongest and fastest hunters form the handle stars, including small Alcor said to represent their dog. The hunt begins in spring when the bear leaves its den – Corona Borealis – but is not finally caught and killed until autumn by which time four of the warriors have fallen behind, including the much heavier, slower warrior, Arcturus. With the bear closest to ground in autumn, its spilt blood is shed over all the forests and plants on earth causing them to turn all shades of red. The skeleton of the bear remains in the sky until the following spring when a new bear emerges from Corona, and the hunt begins again. SQUARE OF PEGASUS, WATER JAR, CAPRICORNUS (PAN), SOUTHERN FISH Let’s turn now to the ‘Square of Pegasus’, part of the constellation of Pegasus itself, which during October rides high to the south during mid-evening and is a most useful ‘signpost’ asterism. In mythology Pegasus is often depicted as the winged steed of Perseus, which sprang from the body of Medusa after Perseus had decapitated her. However Pegasus was actually ridden by another hero, Bellerophon, who was sent on a mission to kill the Chimaera, a fire-breathing monster, part lion, part snake and part goat! The stars forming the ‘square’ are not particularly brilliant, but do encompass a seemingly sparse area of sky and therefore appear relatively conspicuous. Starting from the top left hand star, Alpheratz, travelling clockwise around the ‘square’ we in turn encounter Scheat, Markab and Algenib. Alpheratz is actually the chief star of Andromeda, the body of which extends away to the east and is the jumping off point to locate the Andromeda galaxy, the most remote object visible to the naked eye. By projecting a line diagonally from Alpheratz down through Markab (alpha Pegasi), you will be guided to a zig-zag asterism of stars representing the ‘water jar’, part of the constellation of Aquarius, the Water Bearer. According to one legend this group represents Zeus pouring down the waters of life from heaven. Several stars in Aquarius have names beginning with ‘Sad’, which in Arabic means ‘luck’ (sa’d). Continue on this same diagonal trajectory and you will strike Capricornus, just above the SW horizon. In Greek mythology the constellation was identified with Pan, god of the countryside who could frighten people with his loud shout (origin of the word ‘panic). On one occasion, Pan shouted a warning to the gods that the monster Typhon was approaching and suggested they disguised themselves as animals to elude the monster. Pan himself took refuge in a river, turning the lower part of his body into a fish, while the upper half remained a goat. Let’s now locate Fomalhaut, the most southerly first magnitude star to rise over Britain. Conveniently, the two right-hand stars in the ‘square’ point down almost directly to it just above the S horizon. Fomalhaut marks the mouth of Pisces Austrinus, the Southern Fish, into which the waters of Aquarius pour. The Southern Fish’s northern counterpart – Pisces – occupies a large portion of the sky below Pegasus and Andromeda but is devoid of any notable stars. According to Greco– Roman mythology Pisces was associated with Aphrodite and her son Heros who in order to escape from the monster Typhon jumped into the Nile, turning themselves into fish. SEA MONSTER CETUS From minnows to whales, or a sea monster to be more precise, as we seek Cetus, in legend said to represent the gargantuan Cracken associated with the Perseus–Andromeda saga. Use Alpheratz and Algenib as pointers to locate the whale’s brightest member, Deneb Kaitos or Diphda, which marks the tail of the creature. The head, an irregular loop of faint stars highlighted by Menkar or Alpha Ceti, lies below Aries. The most celebrated object in Cetus is a variable star called Mira ‘the wonderful’, an extraordinary pulsating red super giant star up to 250 million miles in diameter. When at maximum, a period lasting some ten days, Mira is visible to the naked eye and can rival Menkar. Mira’s slow decline to minimum then takes seven months by which time even binoculars struggle to pick it out. The whole period takes 332 days. Scheat and Algenib point down in Mira’s general direction. Why not try harpooning ‘the wonderful’ orange hue of Mira in the coming weeks? Through the eyes of a small child such stories woven by our ancestors brought the starry dome to life, and even now still have the capacity to do so! ◼ |