Star Lore

Have you ever looked at the stars and wondered how great it would be to know which constellations were which? Perhaps you’d like to understand how they can be used to navigate? It may not be something many of us need on a regular basis but admit it, how cool would it be to be able to gaze up on a dark night and amaze your companions with a bit of your knowledge?  Like all skills, once learned, it needs to be practiced to maintain, but it’s not too difficult when the night sky is a regular occurrence and it only takes a few minutes of gazing.  The only risk is a cricked neck!

There are so many pinpricks of light in the sky at night that it might seem difficult to tell which is which.  This was the same for the ancients, so they arranged many of them into patterns that were often linked to animals, monsters, heroes, gods and stories.  These patterns are called constellations and there are 88 constellations that are now recognised.  However, it is not necessary to learn them all.  Actually it is not possible to see them all, because where you are on the planet and the time of year will affect which ones can be visible.  Also, some are just not as easy to see as others, especially if you live in an area with a lot of light pollution.

This first blog on the stars I’ll try to explain the general principles I have used to learn about the night sky and some tips on how to approach night navigation.  I’ll also include an introduction to a few constellations to get you started. 

So, the first thing to address is why some constellations are seen at different times of the night and different times of the year.

Like the sun during the day, the stars seem to move from east to west during the night.  They are not actually moving, it is our planet that is rotating on its axis.  As the night progresses and we rotate, stars we could not see first thing in the evening become visible.  If you stand outside your back door soon after dark and note where one of the constellations to the eastern part of the sky is (Bootes with its bright star Arcturus or Leo with its bright star Regulus are both good for this at the moment) then check back on it every few hours you will get a great idea of the motion of stars through the sky.  You will also start to see constellations that were not visible earlier in the evening as they rise above the horizon and some of the ones you could see disappear.

Not all stars can be seen all year round and there are two main reasons for this. Firstly as the earth moves around the sun during the year, we are looking in different directions into space and this means our view of the sky changes so we sometimes see different constellations.  Secondly the earth’s true rotation period is 23 hours and 56 minutes (and 4 seconds if we’re being pedantic), because we measure time based on a 24 hour day, each day is 4 minutes different than the previous one. This means that the positon of the stars changes slowly move from east to west over the months and as one set of stars sink below the western horizon, another set rises over the eastern one.

Some northern stars will look like they are rotating in a circle around the pole star due to the rotation of the earth.  These are called circumpolar stars – they are always above the horizon.  For us in the UK the major ones will be the stars that form Cassiopeia, Ursa Minor, Draco, Cepheus and Ursa Major (including the Plough).  They can be seen all year round and all night long so are great ones to start out learning.

So before we outline these constellations (one is technically called an asterism) let me explain my main way of learning the constellations.  It is quite simple really, first I learnt the circumpolar constellations as they are easy and constant.  Then I slowly made my way through the sky adding one or two constellations at a time, building up a map where I understood where each constellation lay in relation to the others I already knew.  I did not learn all the constellations but the main ones – the ones that are easy to identify or have particularly bright stars that can be identified.  This was much easier for me than jumping around the sky learning random constellations.  It also helped to learn some of the various stories associated with each constellation, sometimes there are stories that link constellations together which makes it easier to remember them.  Many of the constellations have more than one Greek story associated with them and in some cases they seem contradictory.  But they are usually quite memorable so choose the one you like best to remind you!  Of course, other cultures had their own stories for the constellations too, and once you learn the Greek ones, it can be really interesting to learn ones from other cultures too.

The circumpolar stars are great for learning basic direction finding as well as being a good place to start learning the constellations.  Let us start with Ursa Minor because it includes Polaris – otherwise known as the north or pole star.

Ursa Minor is also known as the little bear and also the little dipper – I must admit to finding it easier to spot as a little dipper.  It is quite a faint constellation of 7 stars and do not be too worried if you cannot see all of the stars, especially if you live in a town.  However, the end star of the little dipper handle is Polaris – the north star.  Our first point of reference for navigation in the northern hemisphere.  Polaris hovers above the earth’s axis and is so close to being above the north pole that it can be used as a direction finder for north.  Just draw an imaginary line from Polaris to the horizon and that will be north.  Just a side note, there is a common misconception that Polaris is the brightest star in the sky, sadly this is not the case, it is the 48^th brightest star but luckily for us, it is the brightest star in that region of the sky so it makes it easy to spot.

We find out just how much of a rogue Zeus the ruler of the Greek gods was from the stories in the skies, and one of the origin stories surrounding Ursa Minor will become a familiar theme as you learn more about the constellations.  Anyway, Zeus fancied a nymph called Callisto who was a follower of Artemis.  In order to ravish her, Zeus transformed himself into a likeness of Artemis and had his wicked way with her.  Being a god, Zeus was super virile and Callisto become pregnant and bore a son who she named Arcas.  Hera the long suffering wife of Zeus, found out and being a jealous wife and vindictive to boot, she transformed Callisto into a bear.  When Arcus grew up, he was out hunting one day and spotted a bear.  Not knowing the bear was actually his mother, he steadied his bow and was about to kill her when Zeus looked down from Olympus and rushing down to stop a tragedy from happening he turned Arcas into a bear as well.  Then with a mighty heave he threw them both into the heavens.  So, now Arcas as Ursa Minor is forever together with his mother Callisto as Ursa Major, our next constellation.

Ursa Major is also known as the great bear who we now know is actually the nymph Callisto.  Ursa Major also includes a smaller group of stars – the Plough – that most of us find easier to identify.  The Plough is actually an asterism, an obvious pattern of stars that are not recognised as a formal constellation, although they often form part of a larger constellation.  Other examples of asterisms include the Square of Pegasus, the Summer Triangle, the Winter Triangle, the Sickle and Orion’s Belt.  So the Plough is named because the 7 stars in it gives us the shape of a plough used to furrow the ground for planting seeds in the spring time.  In the United States it is called the Big Dipper because it looks like a long handled ladle for water – a dipper.  However you call it, the two bright stars at the end of the furrow or bowl of the dipper are known as the Pointers.  Follow these two stars named Merak and Dubhe for 5x the distance between them and you will find Polaris.  As the Plough is very easily recognisable and visible this is perhaps the easiest way of finding Polaris and therefore north.  But, yes there is always a but!  What if there are clouds obscuring the Plough?  Can we find another easier way of finding Polaris? Yes we can use another circumpolar constellation called Cassiopeia which is in a slightly different part of the sky so may not be obscured by clouds.

Cassiopeia was a vain queen of Ethiopia, the wife of Cepheus who sits by her in the sky and mother of Andromeda.  She was rather taken by her own visage and boasted of herself being more beautiful than the sea nymphs.  Poseidon was petitioned by the sea nymphs who sought retribution from the god of the sea.  As a punishment for her vanity, Poseidon sent a sea monster to ravage the land.  Cepheus and his wife Cassiopeia had to chain their daughter Andromeda to a rock as a sacrifice to the monster, who by the way is commemorated in the stars as Cetus.  But that was not enough of a punishment.  Poseidon placed Cassiopeia in the sky sitting on her throne and revolving around Polaris so that each night she would sometimes suffer the indignity of hanging upside down clinging to her chair and in danger of falling off her own pedestal.  There are five stars in her constellation and they look very much like a W – or maybe an epsilon (∑) or M or 3 depending on where around Polaris she lies during the night.  To find Polaris using Cassiopeia is quite straight forward.  Mentally draw a straight line between the two end stars, effectively putting a cap on the W and extend a line at right angles to the cap for twice the distance of the cap and you should spot Polaris.

Cepheus we have already found out was the poor husband of the vain Cassiopeia.  To me this constellation looks more like children’s drawing of a house.  Cepheus unluckily for him, sits very close to Cassiopeia but can be difficult to see because the five stars that make up the constellation are not very bright, perhaps he is used to being in the shade of his wife’s beauty.  Cepheus does not have a great story, except as a sad addendum to the tale of Cassiopeia.  As his kingdom was being terrorised by the sea monster Cetus, Cepheus went to the Oracle of Ammon whose temple was at the oasis of Siwa in the Libyan dessert to seek counsel on how to save his people.  The answer broke his heart because he was told that to pacify the beast he had to chain Andromeda his daughter to a rock at the ocean’s edge as a sacrifice.  Andromeda was rescued by Perseus after doing a deal with Cepheus for her hand in marriage.

Draco.  Despite being in a spot in the sky that should mean it is easy to find, Draco is not easily seen. Part of this is because it is long and sinuous, winding itself around Ursa Minor, and part of it is because the stars are not the brightest.  Draco consists of sixteen stars and the third star from the tail is called Thuban (or Alpha Draconis) and this is fascinating because from 3942BC until 1793BC it was the pole star.  The earth has a slight wobble to it which leads to a change in the orientation of its rotational axis which is called precession.  This leads to the earth’s north pointing to a different part of the sky and hence to a different star for long periods of time.  There are a few different stories associated with Draco.  The one I prefer is that Draco was one of the Gigantes or giants that were a race of beings formed from the blood of Uranus that fell onto Gaia when he was castrated by this son Cronus.  They went to war with the Olympian gods but lost and were buried under volcanoes.  Draco fought with Athena who caught him by the tail and threw him into the cold northern sky where he coiled around the pole star and froze.

So here are five constellations to get you started.  Have a go at identifying them and finding north to start your journey on using them as navigational aids.  As you get to know these and other constellations you will realise that you will be able to understand in what direction north is by the map that is forming in your mind of where the constellations sit in relation to each other.

Mark Sharwood- Apprentice instructor, Woodland Wayer Alumni, Primitive Skills Year Alumni