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Red dwarf
Here's a red dwarf, courtesy of Swinburne University. Such an object might be stable for as long as a trillion years.
http://astronomy.swin.edu.au/cms/astro/cosmos/R/Red+Dwarf
How many red dwarf stars are there in the observable universe (very roughly) and what is their combined mass (even more roughly)?
(Only estimates required but we want to see you working! Well roughly.)