When Will The First Star Go Dark?
“I’m sorry to disappoint you, but there aren’t any black dwarfs around today. The Universe is simply far too young for it. In fact, the coolest white dwarfs have, to the best of our estimates, lost less than 0.2% of their total heat since the very first ones were created in this Universe. For a white dwarf created at 20,000 K, that means its temperature is still at least 19,960 K, telling us we’ve got a terribly long way to go, if we’re waiting for a true dark star.”
Stars live for a variety of ages, from just a million or two years for some to tens of trillions of years for others. But even after a star has run out of its fuel and died, its stellar corpse continues to shine on. Neutron stars and white dwarfs are both extremely massive, but very small in volume compared to a star. As a result, they cool very slowly, so slow that a single one has not yet gone dark in all the Universe. So how long will it take, and who will get there first: neutron stars or white dwarfs? Believe it or not, there’s still enough uncertainty about how neutron stars cool, mostly due to uncertainties in neutrino physics, that we think we know the answer to be white dwarfs – and 10^14 or 10^15 years – but we’re not entirely sure!