By the end of its planetary nebula phase, the sun will have lost most of its mass, and only its dense core will remain. At this point, the sun will become a white dwarf. A white dwarf is very dense because it contains only the heaviest elements fused over its lifetime, but no more nuclear fusion will be taking place. Because there is no more nuclear fusion occurring in its core, the sun will become much cooler in temperature and only give off a fraction of the light it once did. Over time the Sun will stop generating any heat or light. When no more nuclear fusion is taking place, the Sun will end its life as a black dwarf. Scientists aren't sure what this will look like because the process can take trillions of years, and our universe is only 13.7 billion years old.



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The text has been adapted for a 9th grade level. This was originally the hypertext version of a public lecture given on 1997 June 12 at the Perkins Observatory in Delaware, Ohio, as part of the 1997 New Vistas inAstronomy lecture series. It has been updated a number of times since then.The Once and Future Sun by Richard W. Pogge is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License. Based on a work at The Ohio State University Department of Astronomy (www.astronomy.ohio-state.edu)