When will the first star go dark?
It hasn’t happened yet in the entire Universe, not even once.
“End? No, the journey doesn’t end here. Death is just another path, one that we all must take. The grey rain-curtain of this world rolls back, and all turns to silver glass, and then you see it.” -J.R.R. Tolkien
Ever since the first star in the Universe ignited some 13.7 billion years ago, the Universe has been flooded with light. When enough matter — mostly hydrogen and helium gas — gravitates together into a single, compact object, nuclear fusion will take place inside the core, giving rise to a true star. But as time goes on and fusion continues, eventually that star will run out of fuel. Sometimes, the star is massive enough that additional fusion reactions will take place, but at some point, it all must stop. When those stars finally die, however, their remnants shine on. In fact, the Universe hasn’t been around long enough for even a single remnant to stop shining. Here’s the story of how long we’ll need to wait for the first star to go dark.
It all begins from a cloud of gas. When a cloud of molecular gas collapses under its own gravity, there are always a few regions that start off just a little bit denser than others. Every location with matter in it does its best to attract more and more matter towards it, but these overdense regions attract matter more efficiently than all the others. Because gravitational collapse is a runaway process, the more matter you attract to your vicinity, the faster additional matter accelerates to join you.
While it can take millions to tens of millions of years for a molecular cloud to go from a large, diffuse state to a relatively collapsed one, the process of going from a collapsed state of dense gas to a new cluster of stars — where the densest regions ignite fusion in their cores — takes only a few hundred thousand years.
Stars come in a huge variety of colors, brightnesses and masses, all of which are predestined from the moment of the star’s birth. When you create a new cluster of stars, the easiest ones to notice are the brightest ones, which also…