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READER LETTER: Summer Stargazing

READER LETTER: Summer Stargazing

Thursday 03 August 2023

READER LETTER: Summer Stargazing

Thursday 03 August 2023

When the clouds clear, the skies over Guernsey are perfect for stargazing. Jean Dean from La Societe Guernesiaise's astronomy arm gives us the lowdown on when and where to look:

"Late summer with its balmy evenings is a great time to go outside on a clear night and do some stargazing. Find a dark location and let your eyes adapt to the dark – which will take about 20 minutes. Asterisms are groups of stars in the night sky which often are more prominent than the traditional stick figure constellations.

A fun activity is to find some of the summer asterisms.

Figure_1.jpg  summer stargazing la societe

Pictured: Some of the constellations easily visible from our skies are illustrated above. 

Start by finding The Plough – it is shaped like an old fashioned plough or saucepan.

If you join up the two stars on the end of the bucket – Merak and Dubhe – and project the line you will see the Pole Star or Polaris, this is north.

Then look beyond Polaris and find the constellation of Cassiopeia, a wonky “W” shape.

Next find the Summer Triangle which comprises three of the summer’s brightest stars Deneb, Vega and Altair, and spans across three constellations.

Figure_2.jpg  summer stargazing la societe

Pictured: A number of constellations are easily identifiable if you know what to look out for. 

The first constellation, Cygnus represents a swan and is easily recognisable, its brightest star is Deneb which is a white supergiant at a distance of 3,550 light years. 'Deneb' means tail in Arabic, in this case referring to the tail of the swan.

The constellation of Lyra is one of the 48 constellations listed by the 2nd century astronomer Ptolomy and was often shown on star maps as a vulture or an eagle carrying a lyre.

The brightest star, Vega is unmistakable as it is the 5th brightest star in the entire night sky. It is a bluish-white dwarf star that is about 25 light years away and its name is derived from the Arabic for 'swooping eagle'.

Figure_3.jpg stargazing la societe

Pictured: La Societe's guides can help you spot the constellations in our skies.

The constellation of Aquila sits on the celestial equator, it is Latin for 'eagle' and it represents the bird that carried the thunderbolts aloft from Zeus, the almighty Greek god of the sky and thunder. Altair the brightest star in Aquila is a white dwarf and some 16.6 light years distance. Its name comes from the Arabic phrase meaning 'the flying eagle'.

Once you have found the Summer Triangle then look for the Summer Cross which comprises: Deneb, Sadr, Albireo, Glenah Cygni and Al Fawaris. Alberio is quite faint, but it shows up easily with a pair of binoculars and if you look closely, it is actually two stars, one a rich golden colour and the other a vibrant blue.

Also look for Arcturus, which is a bright orange colour, from this you should be able to identify the Kite asterism. Then look to the east and find Alpheratz and the Great Square of Pegasus which will start to gain altitude as the night progresses. Finally, if you look mid-way between the Summer Triangle and Kite then you should be able find the star Zeta Her which forms a corner of the Keystone in Hercules.

A magnificent sight in the summer is the Milky Way arching overhead. 

Many ancient cultures believed that the Milky Way was a bridge between Heaven and Earth. In fact, you are looking along one of the great spiral arms that make up our Milky Way galaxy.

Figure_5.jpg summer stargazing la societe

Pictured: The Perseids meteor shower is always a popular star gazing event.

Spiral arms are home to dust and gas and the main birthplace of stars and planetary systems. If you look to the south, you will see a long sinuous dust lane – the Great Rift – snaking through the band of stars. With a pair of binoculars start in the south and work your way along the Milky Way and you will see dense star clouds in Sagittarius and Cygnus.

A spectacle not to be missed this summer is the Perseids meteor shower which is active between 17 July to 24 August and peaks on the evening of the 12/13 August.

The meteors are from the dusty remnants of the debris trail left by comet Swift-Tuttle which last passed through the inner Solar System in 1992 and will make its next appearance in 2126.

You will find the radiant (where they appear to radiate from) towards the head of Perseus, so look in and around this general direction to see the meteors.

Figure_7.png stargazing la societe

Pictured: There's lots to look at in the skies above us, if you know what to look out for.

The tiny particles, which are no larger than a grain of sand hit the Earth’s atmosphere at speeds of up to 132,000 mph. At these speeds there is compression of the air in front of the meteoroid which heats up causing the bright streak.

The meteoroid itself also burns up and depending on its composition it can display different colours, with the Perseids it is often a vibrant green because the magnesium content.

As we move from August to September the planets Jupiter and Saturn start to appear in the night sky.

With a pair of binoculars, you will be able to make out some of their many moons. This is also the last opportunity for a couple of years to see Saturn’s rings in all their magnificent detail.

As it makes its 29-year journey around the Sun, the view of the rings that we see from Earth changes with Saturn’s season. At one extreme we see the rings face-on, either from underneath or above and at the other extreme edge-on when they all but disappear from view, which is called the ring plane crossing.

Figure_8.jpg stargazing la societe

Pictured: Saturn's rings will be clearly visible this summer and autumn.

The rings, comprise mostly water ice with small fragments of rock and dust and are typically only 9 metres in thickness. There are seven main rings with thousands of ringlets in between.

It is thought they originated from pieces of comets, asteroids and/or shattered moons that were torn apart by the planet’s powerful gravity.

The Cassini spacecraft also discovered that Saturn’s moon Enceladus, which is venting icy particles and gas into space, contributes much to one of its outer rings.

Figure_6.jpg summer stargazing la societe

Pictured: All images provided by La Societe Guernesiaise.

If you wish to see what is in the night sky each month details can be found on the Astronomy Section website.

For those of you with an interest in astronomy and who would like to learn more, why not join La Société Guernesiaise and its Astronomy Section where we can teach you about the night sky and how to use a modern, computerised telescope.

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