Counting stars

This is a great activity for the whole family that you can do from home, whether you live under dark skies or in a town with lots of light pollution.

This year, the campaign runs from 6-14 February.

Participants are asked to count the number of stars they can see in a quadrangle formed by the brightest stars in the constellation of Orion. It is very easy to find in the night sky, with the four brightest stars being the intensely red/orange coloured Betelgeuse (some of you might know this star as Beetle-Juice), Bellatrix (a name Harry Potter fans will recognise), Rigel (the brightest star in Orion that scientists think may be up to 300,000 times brighter than our sun) and Saiph (about 60,000 times brighter than our sun).

Of the four stars, Betelgeuse, Rigel and Saiph are so large that they will end their lives in a gigantic explosion, called a supernova. These explosions throw elements out into space from which new solar systems, like ours, are formed. Bellatrix will have a more sedate end, becoming a beautiful planetary nebula, as will our own sun, with a white dwarf star in the centre.

If you would like to participate, full details of the project can be found at: www.cpre.org.uk/what-we-care-about/nature-and-landscapes/dark-skies/star-count-2021/. Send your results on the CPRE form to add your count to the national results.

In addition, you can also email your results to astronomy.gg@cwgsy.net and we can produce a local light pollution map.

Why is looking at light pollution important?

Most people are familiar with air, water and land pollution but are not always conscious of light being a contaminant. At night time many of us have become very familiar and comfortable with artificial lighting.

At the Astronomical Observatory in St Peter’s, one of the most frequent comments we hear from visitors is: ‘I have never seen the Milky Way before’. It takes people by surprise, as the night sky to so many visitors is just a diffuse orange glow. Telling them they are looking into the very core of our galaxy, some 100,000 light years away, leaves quite an impression.

Light pollution has many hidden effects – it interferes with normal circadian rhythms, impacting human health and immune function. It adversely impacts behaviour in insects and animals. Unnecessary light pollution also wastes energy, which is expensive, and it contributes to climate change.

In Guernsey we are lucky to have many areas where much of the night skies can be appreciated, but there are equally many areas where we could do so much better.

The International Dark Skies Organisation is a great source of information on how we can look to improve the situation (https://www.darksky.org/light-pollution/).

Other objects to look at

Also look to the right and up a little and you will see the red planet Mars. If you look to the left and down a little you will see the brightest star in the night sky, Sirius.

If you watch it for a few minutes, it will appear to flash in many different colours from blue-white-yellow-red. The atmosphere splits the starlight into these different colours, much like a rainbow.

Also, look at the central lower half of the Orion constellation and you might see a ‘fuzzy patch’. This is the Orion Nebula, a mixture of space dust and gas where new stars and solar systems are being formed. If you have a pair of binoculars you will clearly see the nebula and its bright centre, illuminated by a group of stars called the Trapezium Cluster.

The Astronomy Section of La Societe Guernesiaise

The section has a fully equipped observatory, with advanced instruments, including a computerised 16-inch Meade reflector, and a five-inch Takahashi refractor. Members have many interests, including the planets, comets, deep sky objects (e.g. galaxies and nebulae), double stars, celestial mechanics, computers and photography.

• Visit www.astronomy.org.gg to find out more.

• Keep an eye on the weather forecasts for the week ahead. Remember: your safety and health are the most important things, so stay at home for your star counting this year.

• Pick the clearest night for your count, with no haze or clouds, then wait until after 7pm so that the sky is really dark. Turn off all the lights in your house, too, to make it easier to see the stars.

• Looking south into the night sky, find the Orion constellation, with its four corners and ‘belt’.

• Take a few moments to let your eyes adjust, then count the number of stars you can see within the rectangle formed by the four corner stars. You can count the three stars in the middle – the belt – but not the corner stars.

• Make a note of the number of stars seen with the naked eye (not with telescopes or binoculars) and then submit your count at www.cpre.org.uk and by email to astronomy.gg@cwgsy.net.

• Share your experiences (and any photos) with others on social media using #StarCount.

• And don’t forget to check back in the spring to see the national results and how Guernsey compares to other areas.