1 Possible Death of the Sun When the internal forces in a star are balanced the star is stable. Inwards Gravity The Sun is currently in its stable phase. Outwards pressure The stable period has lasted for a few billion years. It should last for a few billion years in the future. The total length of the Sun’s stable period is estimated to be about 10, 000 million Years. When the two forces become unbalanced then the Sun will start to die.

2 Mid-Life Crisis - Red Giant Red Giant Balanced Forces 1. At some point the hydrogen gas begins to run out and the outwards pressure decreases. 2. The star shrinks because gravity is now the stronger force. Red Giant 3. The core is compressed and more complex fusion reaction occur. The outwards pressure suddenly increases. 4 The Sun rapidly expands.

3 Phase Red Giant Red Giant The Sun will expand into a red giant star and engulf the Earth! Red Giant To cause the expansion the outwards radiation/gas pressure must greatly increase . This happens because Helium is fused into heavier elements like carbon releasing much more energy.

4 Star Man → Star Material In fact all the elements in periodic table except Hydrogen and Helium were made inside the CORE of a red giant star. This means that all we are made of star material! As the universe gets older: Amount of Hydrogen Decreases Amount of heavier elements Increases

5 Seeding the Galaxy with Stars The outer layers get so far away from the core that they become ejected from the star. Red Giant A planetary Nebula forms. The elements are pushed out into space to form gas clouds (nebulae) and eventually other stars.

6 The Sun’s Eventual Slow Death Red Giant A small red dwarf star will be left in the centre of the planetary nebula. Planetary Nebula The red dwarf will shrink and heat up forming a white dwarf star. Eventually the white dwarf will slowly cool and fade into a black body called a black dwarf. Red Dwarf White Dwarf Black Dwarf