The Stelliferous Era

The Stelliferous Era, spanning roughly 1-100 trillion years from now, is defined by the continued birth and death of stars and the flourishing of stellar civilization. But all stars eventually die, and the cosmos marches inexorably towards a darker future...

Overview

For much of the next 100 trillion years, the universe will continue to appear largely as it does today, with stars being born from collapsing molecular clouds, living out their lives in main sequence, and dying in nova or supernova, perhaps sowing the seeds of new stellar systems and civilizations.

This is the eon in which the great wonders of the galaxy will be constructed by the sprawling civilizations that arise - Dyson swarms encapsulating stars, vast computational substrates supporting virtual worlds of unimaginable complexity, and perhaps even megastructures binding the spin of supermassive black holes.

But even diamond worlds and artificial suns must ultimately yield to a stark truth - the era of new star formation is finite. With each passing eon, more and more stellar fuel is "permanently" sequestered into remnants - white dwarves, neutron stars, and black holes, while the hydrogen in the interstellar medium grows ever more diffuse. Fewer and fewer new stars will ignite to replace those that burn out.

Decline

After 100 trillion years, only the longest-lived, lowest-mass stars will remain. White dwarves will slowly cool and dim over quadrillions of years until all the galaxy is held in their spectral grip. The Degenerate Era will have begun.

Long before the last star gutters out, the civilizations of this epoch may need to take extraordinary measures to survive, such as:

Stellar husbandry and life extension for their patron stars
Megascale stellar engineering - artificial fusion, feeding stars with harvested interstellar hydrogen
Mass migration towards the densest galactic clusters, where new stars will continue to form
Uploading populaces into virtual worlds of growing computational efficiency to maximize longevity
Harnessing the rotational and accretion energy of black holes and neutron stars

How far can the limits of stellar technology and megascale engineering be pushed to extend the Stelliferous Era? This is likely the single most pivotal question in the history of any civilization, on whose answer their ultimate fate depends.

But eventually, inevitably, the supply of starlight in the universe must dwindle. With each passing eon, the cosmos grows a little darker, a little colder. A long night looms.

Only those who have planned for this epochal transition, who have mastered the physics of degenerate matter, who have built for extreme deep time, who have founded their empires on the bedrock of black holes and neutron stars, will survive to see the next era of the universe. To strive and thrive in a galaxy devoid of light.

"Gather ye fusionable mass while ye may, for the night is long, and the stars, they fade away."