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This shows some of the constellations visible in the previous slide.

The distribution of stars in space is random but we tend to see patterns. The ancients mythologised about the patterns and in this example it is fairly easy to see why. Orion the hunter appears to be confronted by Taurus the bull. Orion even has a bow-shaped arrangement of stars suggesting he is shooting at the bull.

If you go out on a moonless winter's night (in the northern hemisphere) these things are very apparent.

Although we no longer subscribe to the mythology, the patterns are still very useful for finding our way around the sky. Professional astronomers still refer to the constellations to indicate where objects can be found. Today there are 88 constellations, the boundaries of which are defined exactly by the International Astronomical Union (IAU).

The triangular head of the bull is prominent on a dark night. It is a star cluster called the Hyades. If any 2 stars in the sky are picked at random they may lie at very different distances from us, even if they appear to be of similar brightness. But the stars in the Hyades are all at about the same distance from us. Such clusters are important scientifically because the stars can usefully be compared (analysing their light reveals temperature, chemical composition and certain other things).

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