The Night Sky December 2019
Imagine being in a spacecraft launched in 1977. On board you have been asked to take a 90-minute recording of important sounds, speeches and music, together with 118 pictures of everyday life, in the hope that at some point in the future you would be able to describe and explain some of the wonders of your home planet. What would you choose? I wouldn’t know where to start!
The journey ahead would visit the outer solar system, but then you would have no real destination - just an endless discovery of new places further into space than you could imagine. Every day you would send messages back home to tell us what you had seen. Your next encounter would be in 80,000 years, which is our nearest star, and then past that and outward to infinitum. By then, perhaps, the spaceship itself would be the only relic left of the civilisation that had built it.
Science fiction, I hear you say. Well, not quite. Apart from the spacecraft being unmanned, it is absolutely true. Currently on their 41st year of travel, Voyager 1 and Voyager 2 have both broken away from our solar system and are over 13 billion miles away. They have exited the region of space that is affected by our sun and are now in interstellar space.
Amazingly, the spacecraft are sending measurements and observations back to us but sadly in about five years they will both run out of power. They will continue with their payload of information on our world to share with whoever may at some point in the future stumble across them in the vastness of space. It will take another 30,000 years to cover just 1 light year. (Recommend watching: Netflix- The Farthest. Recommended reading: Murmurs of Earth ISBN 0 340 24423 2)
Cassiopeia
The very familiar ‘W’ shape of the constellation of Cassiopeia is high in the sky this month. It is dancing around the North star opposite the equally recognisable partner The Plough (or Big Dipper). When you view Cassiopeia it is set against the Milky Way and a rich source of Deep Sky Objects. It also contains a supernova remnant and this is the strongest radio source in the sky outside our solar system, first discovered in 1947. The first light from the supernova is believed to have reached us 300 years ago. The pattern of Cassiopeia is nothing more than a line-of-sight effect. Each star that makes up the pattern has a vastly differing distance from us. For example, the star in the middle of the ‘W’ is 10 times further away than the star that makes the end of the ‘W’ shape.
It is easy to understand how the night sky, viewed from different places in space, would soon lose its familiar pattern. Indeed, given time, all stars making up constellations are changing their position in relation to each other. Therefore the patterns we have created will become slowly distorted and eventually unrecognisable.
Longest Night
This month contains the longest night (22nd December) - an astronomer’s dream. A personal winter favourite to look out for is the awesome Rosette Nebula. It is a huge circular nebula that is a popular target for astronomers. The image I have included is in monochrome but viewed in colour is a beautiful red rose- like flower.
Impressively it appears to be nearly three full-moons’ width in our night sky although its actual width would take 130 years to cross at the speed of light! It is just visible to the naked eye but its full glory is unlocked with a pair of binoculars or better still, a telescope. Its location in the sky is low in the south-east to the left of the very distinctive star of Betelgeuse in the top left corner of Orion.
Between 10th & 11th December the very bright Venus is visible in the south-west and passes Saturn after sunset.
Full Moon 12th December
New Moon 26th December
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