It’s early September in Tenerife and we have a beautiful night sky to show you.
The Milky Way is still prominent in the night sky in a huge arc starting at the core in Sagittarius and stretching over to Cassiopeia.
The summer constellations dominate the night sky but the winter constellations are beginning to emerge in the eastern sky as the night progresses.
The beautiful Scorpion is in the south with Sagittarius Capricorn and Aquarius further to the west Libra and Virgo are still visible.
To the north we have Cassiopeia and Perseus and the Pegasus all very clear in the beautiful clear Tenerife night sky.
Above us and towards the east we have the flying swan Cygnus The harp Lyra and the eagle Aguila with a perfectly formed small constellation of Delphius the dolphin sitting just below it.
However apart from these beautiful summer constellations that were all part of the 88 constellations named by the ancient Greeks over 3000 years ago there are another group of stars that are a modern day collection of stars called Asterisms. Asterisms can be contained within one constellation or be a group of bright stars from different adjacent constellations.
There are four main Asterisms in the night sky above Tenerife and below are the details .
The Summer Triangle
This is the three main stars of the constellations Lyra Cygnus and Aguila. The top of the triangle is the star Vega in Lyra with Altair the Alpha star in Aguila to the east and below, and towards the west is the main star in Cygnus Deneb.
These three stars known as the summer triangle were used by our ancestors as a guide to the season in which to pick the grapes to make wine.
The Teapot
This is one of my favourite asterisms and lays completely in the constellation of Sagittarius. Its formed from eight brights stars that form the trapezoid of the teapot with a triangular lid two stars to the left form the handle and there is a star to the right that is the spout. Think Mrs Potts in Disneys Beauty and the beast. From the spout of the Teapot flows the steam or milky way as it crosses over to the north. Between the spout of the teapot and the Cats eye double star in Scorpius is located the core of the Milky way our galaxy.
The Big Dipper or Plough
This is probably the most well know asterism its also known as the Big car or in some countries simply the big bear. Its seven bright stars that form the tail and back leg in the constellation Ursa Major the big bear. This is large prominent asterism in the northern sky is also useful to find the north star Polaris which has been used as an aid to navigation for millennia. The two stars at the bottom of the saucepan named Dubhe and Merek point towards Polaris roughly five times the space between these two stars in a straight line lies the North star Polaris. The angle of Polaris and the ground also gives us our latitude above the equator in Tenerife we are at 28 degrees above the equator so its quite low compared to northern Europe at 50+ degrees, so it appears much higher in Northern latitudes. Sailors have been using Polaris for centuries to determine north and their latitude. They used an instrument called a Sextant which is a a giant protractor showing angles with a sliding eyepiece and a level so they eyed in Polaris through the eyepiece with the Sextant level and read of the angle on the protractor. This must have been quite a difficult task on a choppy sea with the ship moving up and down in the waves.
The great square of Pegasus
As the name suggests this asterism lies wholly in the constellation of Pegasus and is the four bright stars that form the body of the flying horse. I personally use this square to find the Andromeda galaxy. By going to the bottom lefthand corner of the square and counting down the two brightest stars then going at a right angle upwards from the second star and the second object you can see is the Andromeda galaxy. This is visible with the naked eye in the dark skies above Tenerife its our closest galaxy at two and a half million light years distant. Andromeda is easily visible with a pair of binoculars but a great deep sky object to look at through our large computerised telescopes.
We hope to see you soon on one of our excursions where we would love to show you these incredible visions in the night sky
Written by Steve Phelps
