A report concerning stars and constellations

The animal's skin was impervious to iron, bronze, and stone. Heracles' arrows harmlessly bounced off the lion; his sword bent in two; his wooden club smashed to pieces. So Heracles wrestled with the beast, finally choking it to death. He then wrapped the lion's pelt about him; it would protect him from the next labour: killing the poisonous Hydra.

As the story goes, the lion found its way to the heavens to commemorate the great battle with Heracles. Yet this isn't all there is to the story. For even in antiquity, long before the Greeks began telling stories, the lion was an ancient symbol of power.

It is said that when the lion chases the constellation of the bull, the spring starts. An intriguing theory, put forth thirty years ago by Professor Willy Hartner describes the result. Briefly put, at about 4000 BC, the Lion is seen chasing the Bull over the horizon, announcing the end of winter and the beginning of spring. I shall quote Professor Hartner's descriptive words:

"The constellation Leo would have been directly overhead, standing at zenith and displaying thereby its maximum power [as it] kills and destroys the Bull trying to escape below the horizon, which during the subsequent days disappears in the Sun's rays to remain invisible for a period of forty days, after which it is reborn, rising again for the first time (March 21) to announce Spring equinox." 

[See W. Hartner, "The Earliest History of the Constellations in the Near East and the Motif of the Lion-Bull Combat" JNES 24(1965)1-16.]

Leo is a fairly compact constellation and, unlike so many other constellations, it is readily recognisable. Alpha Leonis is named "Regulus" because it was seen as the Heaven's Guardian, one who regulated all things in the heavens. While the name Regulus was given by Copernicus, the star was better known in antiquity as Cor Leonis, the Lion's Heart.

Ursa minor (small bear)

Ursa Minor is a fainter version of the Big Dipper (or Plough, in the UK), and is home to the North Star.

The constellation dates from antiquity, and is said to have been introduced by the Greek philosopher Thales around 600 BC.

For as long as ships have sailed the seas Polaris has been an essential guiding star. 

However the Pole Star isn't, as one might think, constant, but rather it changes gradually through several thousands of years. The earth's axis moves very slowly, like a top, completing a circular path every 25,800 years. During this "processional cycle" several stars take turns becoming the Pole Star. I’ll discuss more of this in the course of this report.

Traditionally amateur astronomers have used the constellation as a rough guide on the clarity of the evening's sky. The stars range from second magnitude down to fifth (and even sixth); if these latter stars are clearly seen, it's a good night for viewing.

Are the constellations as they were before and will they still be there in 2000 years ?

I will answer this by asking some questions discussing how fast the stars are moving and how far the ‘constellation stars’ are placed in respect to the earth.

Why are the stars moving?

It’s a common idea that the galaxy has been expanding since the big bang. You can’t tell in which way or from which source the galaxy is expanding because it’s impossible to pinpoint the middle of the galaxy. The galaxy is a weird thing. Pinpointing the middle of the galaxy is like pinpointing the middle of the earth’s surface. Every point could be the middle. So when the universe is expanding it’s stretched and therefore the stars move too.

How can we see that the stars are moving?

To answer this question I’ll have to explain something called the Doppler effect. A physician called Doppler invented it in 1842. It’s the theory that wavelengths become shorter in front of a fast moving object. The Doppler effect occurs almost everywhere, even in our daily life. For example when you encounter a train.

When a object that makes a sound (in this case a train) stands still, the wavelengths are just as they would be anytime, as if you were talking to a friend.

But when the train travels at a high speed, it kind of squashes the sound waves. Be-cause that waves are squashed, they become more compact. Here, it means that the sound will be pitched higher.

It’s true. When you are waiting for a train at a crossing, or if a car is speeding by, or when a fighting-jet is flying over you’ll experience the effect described above. First the sound will be high pitched, and when the object has passed, the wavelengths become higher again and the sound will be lower pitched.

The same goes for other media. In this case the same goes for the light of the stars. We know that the stars are moving. If a star is moving very fast the wavelengths of the electromagnetic rays become more compact. This means that the light will gain more or less energy. The more energy the light gets, the bluer it becomes. The scientific explanation is described below.

I’ve got a Dutch scientific explanation of the Doppler effect formula from a Dutch source, I’ll try to give an English translation.

Hierin is c de voortplantingssnelheid van de golven in de tussenstof, vw de snelheid van de waarnemer ten opzichte van de tussenstof, vb die van de trillingsbron; c, vw en vb worden in dezelfde richting positief genomen

Fw is the frequency in which the receiver sees the light. Fb is the frequency in which the receiver sees the light and the object as if it were not moving. C is the speed of the waves in the space between the object and the receiver. Vw is the relative speed between the object and the receiver and Vb is the speed of the object.

When a star is moving towards are solar system it will appear more blue then usual. And of course when a star is moving away from our sun it will appear redder. If a star is further away, the redshift or blueshift is bigger. This means that stars which are very far away move faster then the stars that our closer to the earth. The stars, which are very far away and because of that, are moving very fast can’t be seen without the help of a telescope. The stars in our constellations aren’t that far away.

Conclusion

When the constellations were made up, they were formed by stars and by star formations, which could be easily recognized. So the stars, which can only be seen with a telescope, weren’t included. This means that the stars in the constellations are ‘close’ to the earth. And when they are close to the earth, they are not moving as fast as the stars, which are further away. Of course they are moving but not so drastically that the formations go through radical changes. Our star formations will stay the same for a couple of thousand years.