After the main sequence period, the amount of hydrogen in the stars core decreases causing the star to fuse helium nuclei instead. (Further explanation for clarification)This releases a lot of energy causing the outer layers of the star to expand. (1 mark) The star has become a red giant. (1 mark)Eventually, this red giant ejects its outer layers and shrinks (1 mark) to form a small, hot white dwarf. (1 mark) White Dwarves are smaller than main sequence stars.Over time, white dwarves radiate energy and their temperature decreases. (1 mark) Eventually, they cool so much they no longer emit radiation. (1 mark) A black dwarf has formed.