Solar System
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Image copyright Sea & Sky

Stars are bright balls of gas floating amongst the darkness of space. They are slightly passive compared to the birth and death processes, which are chaotic, colourful and downright bizarre.

There are many different types and most of the stars in the Milky Way are invisible to the naked eye. The brightest ones usually have some backstory or importance attached to them. For example the ancient Egyptians found the brightest star Sirius to be very important as it was in the sky before the annual Nile floodings that revitalised the desert. Another odd fact, which is a favourite of conspiracy theorists, is that the Egyptian pyramids at Giza seem to line up with a group of stars called Orion's Belt. This idea is known as the Orion Correlation Theory and was devised by Robert Bauval. Many Egyptologists have tried to explain the correlation but the orthodox ones have ignored and dismissed many claims. According to sky planetarium programs, the only time the pyramids were aligned with Orion's Belt was in 10 000 BC. According to archaeologists, it would have been impossible for the Egyptian civilisation being around at that time as there is no evidence. Some still maintain that this idea is correct and might very well be.

Giza pyramid complex         Orion's Belt  
The orientation and size of the pyramids of Giza in Egypt look quite similar to Orion's Belt. Coincidence or deliberate?           Orion's Belt as seen with a small telescope. The third star isn't directly diagonal with the others just like the third pyramid. The brown cloud at the bottom left is the Flame Nebula, a region that is forming stars.  
Image copyright Satellite Imaging Corporation
Image copyright R. Gendler
Regulus Tomb of Thutmosis III   The Ancient Egyptians believed there was a region in space called the Duat where the souls of dead pharaohs went. The symbol of this was the five pointed star. Also the constellation of Orion was used to represent the main Egyptian god, Osiris.
  The ceiling of the tomb of the pharaoh, Thutmosis III.  
One of the brightest stars in the sky is Regulus in the constellation of Leo.
Image copyright S. Faiia
Image copyright R. Croman

Another bright star that was important was Polarus, the Pole Star. This let sailors in the 15th and 16th centuries find north during night time.

The names of stars were given by the Romans, Egyptians, Greeks and Arabs.

Interestingly the closest stars are some of the faintest and can only be seen with telescopes. The closest star is Proxima Centauri at 4 light years away. One light year is a staggering 5,879,000,000,000 miles.

The brightness of a star is called the magnitude. This is measured in numbers. The brighter something is, the lower the number and the fainter something is, then the number is higher. Objects brighter than zero are measured in minus numbers.

The apparent magnitude is the brightness of a star as it is seen in the sky. All stars seem to have an illusion of being at a fixed distance but they are all at different distances. This means that the 'true' brightnesses of stars are different. This is known as the absolute magnitude, which is a measurement of the luminosity of stars.

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