At what point in time will the sun become a black dwarf? A trillion years?
Longer than a trillion years.
"Barrow and Tipler estimate that it would take 10[sup15[/sup] years for a white dwarf to cool to 5 K; however, if weakly interacting massive particles exist, it is possible that interactions with these particles will keep some white dwarfs much warmer than this for approximately 1025 years."
(And WIMPs are a rather good bet)
When I read the title I thought of gary coleman for a split second.
Yeah I think its a trillion years
Depends on how you define "black" since WIMP heating, according to Adams & Laughlin's estimates, will heat a white dwarf to 63 K, making it still glowing in IR. But if we're talking below the temperature at which an object glows with its own heat, roughly 800 K, then a white dwarf that's presently at ~4000 K will take about ~2 trillion or so years to cool to that point. An isothermal ball would cool quicker (just ~1 trillion years), but real white dwarfs have an opaque outer crust which slows down the escape of heat.
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