Out & About Winter 2018

STAR GAZING

Newbury Astronomical Society’s NIC FLEET presents a round-up of some of the night sky highlights to look out for during the winter months, including spotting Venus

Close up of Orion Nebula

Orion the Hunter O ne of the most easily recognisable constellations in the night sky is Orion, the Hunter. You can see it low

Venus – our Christmas Star The planet Venus has now moved into the morning sky and will be visible low down in the south east just before dawn throughout the Christmas period. There are many theories about whether the Star of Bethlehem was a real astronomical object. If it was, it must have been something extraordinary, as our ancestors were familiar with the ordinary movements of the stars and planets. Some have suggested it was a comet and Halley’s Comet was recorded by Chinese astronomers in 12BC, which is too early, and another faint comet was seen in 5BC, but comets were considered bad omens, so unlikely to herald the birth of a king. The sudden violent explosion of a star, known as a supernova, could have caused a bright new star to appear in the sky; however, if this star had been in our galaxy, we would almost certainly be able to see its remains. Also, Chinese astronomers were always on the lookout for such ‘guest stars’, but didn’t record any at the right time. The most popular theory is that the Three Wise Men were astrologers and could have interpreted a rare alignment of the planets to signify the birth of a king of the Jews. One possible alignment happened in the year 7BC when the planets Jupiter and Saturn came close together in the constellation of Pisces, the Fish. Another happened on April 17, 6BC, when the moon passed in front of the planet Jupiter at sunrise, an occurrence said to foretell a royal birth. Lastly, on June 17, 2BC, the planets Venus and Jupiter came very close together near the star Regulus in the constellation of Leo the Lion – the king of the beasts. Venus and Jupiter will again be close together, sparkling away low down in the south east, just before sunrise between January 20 and 26, 2019 – but this time they will be in the

down in the east after sunset at the beginning of December and by the end of January it will be high in the southern sky all evening. It’s shaped like an hourglass, with four bright stars at the corners marking Orion’s shoulders and legs, and a row of three bright stars in the middle forming the hunter’s belt.

Orion through clouds

Most of the bright stars in Orion are blue-white super giants, much bigger and hotter than our sun. However, the top left-hand star, called Betelgeuse, looks distinctly orange. This is because it’s a huge red supergiant, about 10 times as massive as our sun, but only around half as hot. It’s so big that, if you put it where the sun is, its outer layers would reach out as far as Jupiter – and the Earth would be orbiting inside it. When it runs out of fuel, sometime in the next few million years, it will probably explode as a supernova. Luckily for us, it’s too far away to damage the Earth, but it could become as bright as the full moon for a few weeks and would be a spectacular sight. Below the belt of Orion is another line of stars marking the hunter’s sword. The middle ‘star’ in the sword looks slightly fuzzy, and this is because it’s not a star at all – it’s actually a huge cloud of dust and hydrogen gas called the Orion nebula. Inside it are around 2,800 newly-formed stars which heat it up and make it glow. Our own solar system formed in a similar cloud of dusty gas around 4.6 billion years ago. Orion is a great ‘signpost’ constellation for finding others. If you follow a line through the belt stars up and to the right you’ll come to another red giant star called Aldebaran in the constellation of Taurus, the Bull. If you follow the belt stars down and to the left you’ll find the brightest star in the night sky, Sirius – the Dog Star.

constellation of Ophiuchus, the Serpent Bearer, which has no connection with royal births. Whatever the explanation for the Star of Bethlehem, you can look out and enjoy our very own Christmas Star this winter.

Jupiter & Venus are just a cat’s ears apart

newburyastro.org.uk

Pictures: John Napper, Steve Knight, Richard Fleet

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