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The Winter Night Sky When we try to find our way around the constellations of the night sky it is easy to become frustrated at the countless stars we see, but if you persist, not only will you find it much easier than you first thought, you will also be rewarded with a wealth of knowledge that will grow and grow every time you look to the heavens. Planets, nebulae, Galaxies and star clusters as well as the ability to identify constellations, will all be within your grasp just by following a few simple steps. Firstly consult a Star map, which will give you names and shapes of constellations; one of our monthly night watch sheet’s will get you started, find one of the most prominent of these shapes in the sky, for instance the Plough then draw an imaginary line to the next constellation find out what this constellation is on your star map, and repeat this process over and over and soon you will be immersed in a world of modern fact and ancient myth. As we move around the Sun, the tilt in the Earths axis causes our seasonal changes, and we see different constellations in the night sky throughout these seasons. For instance during the summer months the constellation Cygnus is directly overhead but during winter it is nowhere to be seen. Cygnus is still overhead during winter only now it is daytime and so it is drowned out by the daylight. There are always fascinating things to see in the seasonal night sky, but winter is particularly rich and diverse with interesting objects for us to see. Let us look at some of these objects as we take a journey of wonder and imagination around the winter night sky. We start off with a constellation that most people know, the Plough. Some people think the Plough looks like an old saucepan; here is the curved handle and here is the pan. It is called a circumpolar constellation, which means that it never sets below the horizon for us Northern hemisphere observers. If you look closely at this star in the handle of the Plough, you will see that it is actually two stars which orbit around each other called Mizar (my­zar) and Alcor and this type of star is called a binary or double star. These two stars are called the pointers because if we draw an imaginary line this way, we come to the North Star; this Star always points in the direction north. If we continue our line this way we come to another star pattern, Cassiopeia, who in Greek myth was said to be a powerful but vain Queen of Ethiopia who was punished for comparing her beauty to that of the Gods This constellation is easy to recognise as it looks like a “W” shape. If we come back to the pointers and strike a line in the opposite direction from Polaris, we eventually come to the constellation Leo. Leo, meaning “Lion” is one of the few constellations that actually resembles its description.
Greek myth tells us that Leo represents the Nemean (ne­mee­an) Lion from the story of Hercules, who had the unenviable task of destroying the creature with his bare hands, as its skin was impervious to weapons. Eventually after fighting a terrible battle with the Lion, Hercules managed to wrap his enormous arms around the throat of the Lion and finally slay the beast. Afterwards Hercules skinned the Lion and wore the skin like a suit of armour in future battles. This star called Regulus (regg­u­lus), is the brightest star in Leo and is spinning so fast, that it is wider at its equator than at its poles and if it were to rotate just 16% faster, the force of gravity would not be able to keep it from tearing itself apart. Let us continue our imaginary line this way until we come to these two bright stars called castor & Pollux in the constellation of Gemini. Castor and Pollux are the two "heavenly twin" stars giving the constellation Gemini its name. Ironically the two are nothing alike, while Castor is a hot white star in a group of six; Pollux is a single cooler yellowy­orange giant . In Greek mythology Castor and Pollux were the offspring of the beautiful mortal Leda (lee­da), and the God Zeus who was disguised as a swan and as a result the twins sprang from an egg. Helen of Troy, famous as the cause of the Trojan War, was their sister, and the twins engaged in many adventures, including becoming two of the Argonauts, who led by Jason, went in search of the famed Golden Fleece. Now can anyone guess which constellation this is? Of course, this is “Orion, the hunter”. Orion’s brilliant stars are found on the celestial equator and are visible throughout the world, making this constellation globally recognized. These are his shoulders, these are his feet and these three stars make up the famous Orion’s belt. This Star called Betelgeuse, meaning “armpit of the giant” in Arabic, is a red giant so large that if put in place of our sun, it would almost reach the orbit of Jupiter, but the brightest star in this constellation is Rigel at the left foot of Orion. Rigel shines with the brightness of 40,000 Suns and is a blue supergiant in the process of dying; fated to explode in a huge supernova. Stars like Rigel live fast and die young and the saying “the light that burns twice as bright burns half as long” couldn’t be more appropriate. Orion was said to be the powerful son of Neptune, God of the sea and was known for his hunting prowess. He would boast that he could hunt and kill any creature along with his favourite hunting dog, Sirius. Follow a line down from Orion’s belt and we come to Sirius. Sirius is the brightest star in the whole night sky and belongs to the constellation Canis Major, meaning “Great dog”. If we follow the line of Orion’s belt upwards, we come to another supergiant star Aldebaran, which marks the eye of Taurus the bull.
Aldebaran is an old star that has burnt up its hydrogen and is now fusing Helium to make heat and light. The word Aldebaran comes from the Arabic word meaning “the follower” and refers to the way the star follows the Pleiades around the night sky. This faint patch of stars at the shoulder of Taurus is the Pleiades cluster, or the seven sisters and people with good eyesight can usually make out seven stars with the naked eye, but if we look closely, there are actually hundreds in this patch of sky. According to the ancient Greeks, the Pleiades were seven sisters, daughters of Pleione (play­own­ee) and Atlas who was condemned by Zeus to support the world on his shoulders. If the sky is dark enough and you are away from city lights, you may just be able to make out a misty faint band of stars extending across the sky this is our home galaxy, the Milky Way. The Milky Way is a spiral galaxy with over 100 billion stars and the Sun and its retinue of planets are in one of the outer spiral arms of our galaxy. It takes the Sun roughly 200 million years to complete a single orbit around the Milky Way galaxy. Occasionally you may see a streak of light flash through the sky; this is a Meteor or shooting star. Meteors are mostly no bigger than a grain of sand, and while they are travelling through space at incredible speeds they come into contact with our atmosphere which causes friction which in turn heats up the tiny rock until it starts to burn. Periodically we have meteor showers, with hundreds of meteors emanating from the same apparent point in the sky. These showers typically last from a few hours to several days and are caused by debris being expelled by a comets tail. Each day as many as 4 billion meteors, mostly miniscule in size, fall from space. Occasionally, one of these Meteors will survive to hit the ground. These are called Meteorites. You can see some meteorites on the space gallery after the show. The night makes way for the daytime and the only star we can see now is our life giving Sun. The Sun will one day run out of fuel, then start to expand so much that it will swallow up the inner planets including the Earth; but don’t worry, this won’t occur for a couple of billion years. Who knows, before that happens humans may have colonised dozens of worlds in a fraction of that time, especially when you consider how far we have come in the past fifty years. Don’t forget to pick up one of our monthly night­watch sheets on your way out which will not only show you where and when you can see passing planets but also show you which constellations you can expect to see amongst “The Winter night sky”.