An introduction to towpath astronomy

By Brian Jones

 

ASTRONOMY is by far the oldest of the sciences and humans have been gazing at the night sky since well before recorded history, although it is only in relatively recent times that we have had something more than the unaided eye to help us in our quest for knowledge of the universe.

During the early 17th century, when Galileo and his contemporaries first turned their telescopes to the night sky, they witnessed for the first time sights that had hitherto been hidden from human view.

Telescopes can indeed reveal many wonders scattered throughout the night sky, although we can spend many interesting and fruitful hours gazing at the heavens with nothing more than the unaided eye.

On clear and moonless nights we can see anything up to 3000 or more stars with no optical aid whatsoever. Street lighting and other forms of light pollution do, however, take their visual toll, and stargazers often need to travel to places outside cities and towns in order to witness truly dark skies.

It is therefore fortunate for canal boat users that they often find themselves moored at locations well away from city lights. Here they can truly take on the mantle of ‘towpath astronomers’ and witness skies that are as dark and impressive as they are meant to be.

One of the most famous and easily recognisable star patterns is the Plough, the distinctive shape of which is easily located lying low in the northern sky during November and December evenings. Shaped rather like a gigantic heavenly spoon, the Plough is actually part of a much larger star pattern, or constellation, called Ursa Major (the Great Bear) although the rest of the stars forming the Great Bear (not shown here) are all comparatively faint. However, the stars which make up the Plough and which represent the hind quarters and tail of the bear stand out quite well.

As with many of the stars that we see in the sky, the names of those in the Plough are quite interesting and varied. For example, the star Dubhe derives its name from the Arabic ‘al-dubb’ meaning ‘the Bear’ whilst Merak comes from the Arabic for ‘the Groin (of the Great Bear)’.

Megrez derives its name from an abbreviation of the Arabic for ‘the Root of the Tail’ and, staying on the theme of ursine body parts, the star Phekda derives its name from the Arabic fakhidh al-dubb al-akbar’ meaning ‘the Thigh (of the Great Bear)’. If nothing else, these names are certainly descriptive!

If you take a close look at the star in the middle of the Plough ‘handle’, you will see that this is actually a pair of stars comprising Mizar – the brighter of the two – and a nearby companion star Alcor. Both Alcor and Mizar can be made out individually if you have very keen eyesight and the sky is really dark and clear, although binoculars may be needed to bring the pair out well.

Powerful binoculars, or a small telescope, may enable you to see another, much fainter, star forming a triangle with Alcor and Mizar. This star bears the somewhat-clumsy title of Sidus Ludoviciana (Ludwig’s Star) and was named as such by the eccentric German astronomer Johann Georg Liebknecht in 1723.

Spotting the star in his telescope and believing that he had discovered a new planet, Liebknecht named it in honour of his sovereign and patron the Landgrave Ludwig of Hessen-Darmstadt. The ‘discovery’ was quickly proved to be erroneous, although the imaginative name Liebknecht gave to the star remains to this day.

In the next article for the Towpath Astronomer, we will discover how to locate Polaris, the Pole Star, by using two of the stars in the Plough as pointers. In the meantime, although winter evenings are fairly chilly, why not brave the elements and venture onto the towpath to seek out the celestial Plough and take a closer look at Liebknecht’s spurious planet? Happy stargazing!

In the next article for the Towpath Astronomer, we will discover how to locate Polaris, the Pole Star, by using two of the stars in the Plough as pointers. In the meantime, you can check out my blog Starlight Nights which can be found at www.starlight-nights.co.uk  Although winter evenings are fairly chilly, why not brave the elements and venture onto the towpath to seek out the celestial Plough and take a closer look at Liebknecht’s spurious planet? Happy stargazing!

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