In the last piece I wrote on this subject, it was about the night sky in Autumn, actually November. Now we are in Winter, early January. And the view up there is certainly different from what it was in November. As I’ve mentioned before, these pieces about the night sky are really intended for children, but adults are welcome!
Orion
The night sky is now dominated by Orion - the hunter. As usual, this goes back to ancient Greek myths, although the details of this particular myth aren’t very well known today, so let’s just concentrate on the stars.
The most obvious way of finding the constellation is to find what looks a bit like a question mark, facing backwards. The upper part of the question mark consists of three stars - all in a straight line, so not quite like a question mark as they don’t loop over. They are Orion’s belt, according to the myth. The lower part of the question mark also consists of three stars. They are said to be his sword.
The belt and the sword are just the central part of the constellation. The whole thing has been likened to an hour glass or - it seems to me - a big “H”. Going back to the Greek myth, the stars at the top of the H are his shouder or armpit or maybe the club he uses to kill all the animals he comes across. The lower ones are his feet. These stars are all definitely worth looking out for.
Betelgeuse
The star that is top left is Betelgeuse - it’s best to pronounce it “betel juice” not “beetle juice”!
There are two things about Betelgeuse that make it worth seeing. The first is its size. It’s the largest star you can see anywhere. They say that, if it was at the centre of our solar system in the place of the Sun, it would absorb all the inner planets, that is Mercury, Venus, us the Earth, and Mars, because it itself would extend beyond the orbit of Mars. Why, you may ask, doesn’t it look bigger, or at least not much bigger? The answer is because it’s so far away - it is about 500 light years away, meaning that the light from it started coming to us in the reign of Henry VIII.
Red Giants and Supernovae
The other mind-blowing point about it is that it’s probably coming to the end of its life. It’s a so-called Red Giant. It’s interesting to see if you can detect the red in it - on a clear night you should be able to - just!
Stars have a life-cycle, which I’m going to describe - probably over-simplifying it a lot. They start by emerging from a cloud of interstellar dust. They consist largely of hydrogen exploding and continuing to burn away at unbelievably high temperatures. This is what our Sun is busy doing right now. This goes on for millions of years until they start to use up their supply of hydrogen. Then, towards the end, curiously, they expand and become giant stars, changing colour. In the final stage they become red - hence the description “Red Giant”. And then, right at the end, they explode and effectively disappear from the night sky. This catastrophic event is called a “supernova”.
When it happens in the case of Betelgeuse, it will be very visible here on Earth. They reckon that the star - it would still look like a star - would be so bright that it would be visible during the day, probably brighter than a full moon. Astronomers think that a Betelgeuse supernova might happen soon - which, in astronomical terms, means any time in the next 100,000 years! But it could be tomorrow. Remember that, if it does happen tomorrow, it will really have happened 500 years ago because of the distance involved.
There are records of various sightings in the past of “new stars” that suddenly appear and then mysteriously disappear. These must have been supernovae. Maybe there was one at the time of the birth of Christ, giving rise to the stories of the three wise men following the star. The last one in our galaxy was in 1604. Maybe we are due for another.
Rigel
The other giant star in Orion is Rigel - pronounced to rhyme with Nigel, not regal. It’s down at the bottom on the right, one of the feet.
Again, it’s enormous, though not quite as large as Betelgeuse. Again, it’s many hundreds of light years away. It’s slightly brighter in the sky than Betelgeuse. It happens to be a “white giant”, meaning that it is also coming to the end of its life. Stars go white before they go red. So, in a few million years, it will presumably become a red giant. And then explode as a supernova, but sadly we won’t be around to see it.
The Orion Nebula
Before we leave Orion, we ought to take another look at his sword. There seem to be three stars. Actually, it’s more interesting than that. The middle one isn’t a star at all. It is an amazing cloud of interstellar gas, in which new stars are actually now being formed. If you manage to see it through binoculars, it does look like a blur rather than a normal star. It’s called the Great Orion Nebula.
So, in Orion, we see stars at various stages: new ones in the Orion Nebula; and old ones in the shape of Rigel and Betelgeuse. Our own Sun completes the picture. It is middle aged - if that’s the right expression for something that is already over four billion years old. It’s got a few more billion years to go. Luckily!
We now need to move along from Orion. Next stop, the Dog Star.
The Dog Star
First, how to find it. Orion’s belt is very useful. You draw a line in your mind extending the belt down to the left. You then get to the brightest star in the sky. It’s proper name is Sirius, although people have called it the Dog Star since at least Greek and Roman times. It’s the main star in the constellation of Canis Major, Latin for the Big Dog.
Back in the days when people thought that stars affected all sorts of things on Earth, the Dog Star was one of the most important in the sky. The ancient Egyptians watched out for it rising in the east just before dawn on the first day of summer. This meant that the waters of the Nile were about to rise, which was pretty important if you happened to be an Egyptian farmer. They called the star the “Nile Star” and various temples were built so as to align with it.
Later, in Roman times, they connected the Dog Star with the scorching days of high summer. Sirius apparently takes its name from the Greek for scorching - one of the few major stars that isn’t named by the Arabs. Some people (not including me, frankly) still talk about the “dog days” of late summer. It all goes back to the superstitions surrounding the Dog Star and Canis Major. Frankly, I find it a bit odd that our ancestors associated it with summer, whereas we think of it as something to see in winter.
Canis Minor
We should take a quick look above the Dog Star in order to find a pair of stars. They are part of Canis Minor, the little dog. You can find it by drawing another line in your mind, this time to the left from Betelgeuse and the other star at the top of the “H”.
The brightest of the pair is Procyon, also from the Greek, meaning “before the dog”. It rises in the dawn just before the Dog Star, so those who were anxiously waiting for the Dog Star were presumably happy to see Procyon paving the way.
Gemini
Moving on upwards, you can easily see another pair of stars. Using Orion to find them, draw a line from Rigel through Betelgeuse and continue upwards.
The pair are Castor and Pollux. They seem to have been very important to the Romans and probably others - the remains of a temple to them still exists right in the centre of Rome. But the myths are most confusing. They were twins - hence Gemini, Latin for twins. Some legends say that both were sons of Zeus, the king of the gods. Others say that one of them had another father. Tricky stuff if they were twins! They all say that their mother was Leda, who Zeus made friends with disguised as a swan - as depicted by Leonardo da Vinci and others.
One interesting thing about these stars is that Castor is in fact six stars, or rather three double stars. However, needless to say, you can’t see that without very powerful telescopes.
The Seven Sisters
We now go in the other direction from Orion. Again using the Belt as a sign post, we can find a very obvious cluster of stars called the Pleiades or, slightly curiously, the “Seven Sisters”. You draw a line from the Belt towards the upper right side. It’s now very high in the sky.
The curiosity is that normally you can only see six stars. Without a telescope or binoculars, it’s frankly a blur. If you look with binoculars, it’s very different. You can certainly see the six stars, in the shape of a saucepan or, as some say, a teacup. If you look even more carefully, you may be able to see more. With a telescope you can apparently see many more. There are in fact hundreds of stars in the cluster. So why seven?
It’s a mystery. It’s possible that in ancient times another of the stars was more visible than it is now. Who knows? My theory is that our ancient ancestors had a fixation about the number seven (it’s still a lucky number) and managed to persuade themselves that they could see seven, perhaps indeed when one of the stars was more obvious than it is today. Think of other sevens: there are seven days of the week (for no obvious reason); seven wonders of the world; seven deadly sins; the seventh seal, opened at the end of the world according to the Book of Revelation in the Bible; and more recently, the Magnificent Seven and even 007 with his licence to kill. And, come to think of it, the Seven Sisters on the coast of England near Eastbourne.
Occultation
And finally, over to my brother. He has a memory going back to his school days that relates to the giant star Aldebaran, which is very visible at this time of year. It’s between Orion and the Pleiades - in the constellation of Taurus, the Bull.
The headmaster of my brother’s prep school had befriended the great amateur astronomer, Patrick Moore (later Sir Patrick Moore, but not back then). For those too young to remember him, he did a television series called The Sky at Night that ran from 1957 till his death in 2012 - longer than any other documentary series anywhere in the world, apparently (I can believe it). The headmaster had persuaded him to give talks at the school. He also managed to persuade him to let a group of boys, including my brother, then aged about 11 or 12, to go to Patrick Moore’s observatory to join a group of university students to see an “occultation” of Aldebaran. This needs some explanation.
Aldebaran is on the Ecliptic, which, as I’ve described before, is the path that the Moon and all the planets follow as they go across the sky. This means that sometimes, not always, the Moon will get in front of a star on the Ecliptic, which seems to make the star suddenly disappear. This is called an “occultation”. It’s best to observe it when the Moon is not full. When the part of the Moon that we can’t see gets in front of the star, the star seems suddenly to be switched off, only to be switched on again when the Moon passes on.
The boys were driven over to see all this in the middle of one night. My brother has had a keen interest in astronomy ever since being introduced to it by the great man.
Tony Herbert
20 January 2024
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