September 2018
The Night Sky
The stories that are told about the patterns seen in the night sky are not exclusive to western culture. However, Greek Myths are familiar and well documented. These tales cleverly orientate the positions of what would be random white dots set against a black sky.
So during September, looking almost directly above you is what looks like a large W shape overhead. This is the constellation of Cassiopeia named after a queen, wife of King Cepheus who ruled Ethiopia. A legend exists that she proclaimed her daughter (Andromeda) to be more beautiful than the sea-nymphs. This upset the sea-god Poseidon who sent a massive wave to awaken Cetus the monster to defend the honour of the sea nymphs by eating the young people of the country! The only acceptable alternative was to sacrifice Andromeda, who was chained to the rocks, to the monster. Fortunately, she was saved by Perseus (arriving on the horse Pegasus) a now familiar figure to regular readers of these articles. All of these famous characters can be seen laid out above your head around this famous constellation. It is all collectively called the Perseus family group.
We Are Stardust
Looking closely at Cassiopeia you will see a central star that is believed to be over 50,000 times brighter than our sun. In relatively recent history two other stars within the constellation have exploded into super-novae. This is the point at which a star ends its life in a gigantic explosion. When Super-novae happen, many of the elements that are crucial to life as we know it are formed under intense and unimaginable forces. Indeed, stars during their life and death are responsible for the creation of the heavier elements that are part of us all, echoed in a popularised phrase of the 60s and song line ‘we are stardust’. It is incredible to think that part of us all have been created by elements that are only formed when stars die. Equally incredible that they then are distributed across space in such a way that they merge to make us!
Andromeda.
Andromeda has its own constellation and it contains our nearest major neighbouring galaxy, M31 appropriately called the Andromeda Galaxy. It is very similar to our own home galaxy, the Milky Way, and is the most distant object visible to the naked eye and at 2.5 million light years away, that is a long way! At the time when the light set off from this galaxy here on earth we were making stone tools. If you do see get to see Andromeda the light that enters your eyes has been travelling since then. It contains at least 200 billion stars. In the 1920s it was thought that our Milky Way galaxy was all there was out there. It wasn’t until 1925 that a man called Edwin Hubble (of the Hubble telescope fame) discovered that certain fuzzy patches in the sky were far too distant to be in our own galaxy. This finding was very radical as suddenly our universe became much, much bigger. On a clear, moonless evening in Embsay it is possible to see the central part of the galaxy with night adapted vision (see last month’s article) but it stretches much further across the sky and with binoculars or telescope you will see an oval shaped galaxy clearly, provided you know where to look. See my diagram. I’ve included a 200 second exposure I took of it last year through a telescope. The galaxy is in fact on a collision course with our own and are approaching each other at about 70 miles per second. Together they will form a larger merged elliptical galaxy at some time in the distant future….in billions of years time.
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