The Night Sky
October 2021
The Pleiades and Hyades.
Looking East this month, half way up in the night sky, sits the glorious Pleiades. You can see them clearly with the naked eye and appear as a very closely grouped set of stars that seem to glisten like an open jewellery box. They are also known as M45 or The Seven Sisters. What we are observing is an open cluster of over 1000 stars, six or maybe seven of which can be seen with the unaided eye. Unsurprisingly, because of their prominence, they appear in many cultures and many legends and myths surround the cluster. One legend from the native Americans has it that seeing five stars you have normal eyesight, but seeing all seven you had the sight of a warrior. The Greek myth is that seven daughters of Atlas (busy holding up the sky!) were seen by a hunter (Orion) who chased them, then Zeus intervened by placing them in the sky. Over the next few months Orion becomes visible above the horizon and his belt, the three central stars, clearly point towards those poor daughters he is said to be chasing!
Photo Jim Thommes
An astronomer in 1761 calculated that the chances of so many prominent stars in the Pleiades being aligned together was one in half a million. He then concluded that they all must be physically related somehow. Nowadays we know that they are locked together moving through space but eventually will disperse.
Just below the Pleiades cluster, but currently above the horizon in the East is what looks like a small side-on ‘V’ shape. The bottom part of this contains a very bright star called Aldebaran. This area is called the Hyades cluster, again containing many hundreds of stars, the brightest form the head of Taurus the bull. Although Aldebaran appears to be part of the cluster of stars in this area it is just a trick of the eye and is located in a different region of space.
Looking East from Embsay on 6th October (New Moon) at 10pm
Aldebaran is a red giant and our own sun will become such a star one day. It is a dying star which has expanded to engulf any inner planets. When this phase is complete it will have exhausted all of its fuel and its outer layer will be blown away. It will then shrink to become a white dwarf. Currently Aldebaran has expanded so that its outer core is 44 times that of our sun.
But it is still not a massive star compared to others!
Diagram-Dave Jarvis
Other things to look out for this month are early evening Venus in the South West (9th October) and Jupiter plus Saturn low in the SE (14th October).
Clear Skies
Milan Davidovic
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