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Boardworks Ltd 20111 of 19 Stars Slide 2 Boardworks Ltd 20112 of 19 Slide 3 3 of 19 Boardworks Ltd 2011 A star is powered by nuclear fusion reactions in its core. In the Sun, and in most stars, hydrogen atoms fuse together to form helium. This provides the energy for life on Earth. What powers a star? Each second, the Sun produces 4 10 26 joules of energy. It would take 2,000 million nuclear power plants a whole year to produce the same amount of energy on Earth. Nuclear fusion involves light atomic nuclei joining together to form heavier ones. Each fusion reaction produces a small amount of energy, but there are billions of reactions per second. Slide 4 4 of 19 Boardworks Ltd 2011 However, not all elements are made in the early stages of a stars life. Some of the heavier elements are only made when a star explodes at the end of its life. Nuclear fusion in stars produces new atoms. How are elements made? When all the hydrogen has been used up, other elements are fused together to make the heavier elements of the periodic table. In the early stages of a stars life, nuclear fusion mainly produces light elements such as helium. Slide 5 5 of 19 Boardworks Ltd 2011 Heavy elements on Earth Slide 6 Boardworks Ltd 20116 of 19 Slide 7 7 of 19 Boardworks Ltd 2011 The life cycle of a star main sequence star neutron star black hole Every star goes through a life cycle. A stars life cycle is determined by its size. red super giant red giant white dwarf super nova black dwarf Slide 8 8 of 19 Boardworks Ltd 2011 How do stars begin and end? Slide 9 9 of 19 Boardworks Ltd 2011 Life cycle of small stars Slide 10 10 of 19 Boardworks Ltd 2011 What is a supernova? Slide 11 11 of 19 Boardworks Ltd 2011 After a really massive red giant collapses in a supernova explosion, it leaves an object so dense that nothing, not even light, can escape its gravitational pull. Some scientists believe that there are black holes at the centre of galaxies. If light cannot escape from a black hole, then how can a black hole be observed? How are black holes formed? The end of the life cycle of really massive stars is different to that of massive stars. This is called a black hole. Slide 12 12 of 19 Boardworks Ltd 2011 How can a black hole be seen? Slide 13 13 of 19 Boardworks Ltd 2011 Life cycle of large stars Slide 14 14 of 19 Boardworks Ltd 2011 Terms about the life cycle of stars Slide 15 15 of 19 Boardworks Ltd 2011 Stars life cycle summary Slide 16 Boardworks Ltd 201116 of 19 Slide 17 17 of 19 Boardworks Ltd 2011 Glossary Slide 18 18 of 19 Boardworks Ltd 2011 Anagrams Slide 19 19 of 19 Boardworks Ltd 2011 Multiple-choice quiz