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Week 6: Classifying the stars

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The constellation of Orion as seen from Tenerife. The four bright stars at each corner and the three stars of Orion’s belt range from magnitude 0.15 (Rigel) to magnitude 2.4 (Mintaka). Many fainter stars can be seen within and around Orion, with brightnesses ranging from third to sixth magnitude. At the lower left is the bright star Betelgeuse which is reddish in colour, with a bluer star Bellatrix above and to the right. These two stars form Orion's shoulders. To the right of the belt is the bright blue-white star Rigel, with the slightly fainter star Saiph below. Saiph and the three stars of the belt are more neutral in colour.