At least, in universe time?
Research over the past 30 or so years has revealed that the formation of stars across the universe reached an extended peak of activity roughly 10 to 11 billion years ago.2 Since that epoch, while new stars are certainly still being produced, the rate of production has lessened dramatically. So much so that it appears that the great majority of stars that the universe will ever make—perhaps 95 percent of them—have already been made.3 The future is one of ever-dwindling numbers of stellar newborns, punctuated by occasional flurries as galaxies merge or other triggering events occur.
But there’s a big puzzle here. Exactly what puts a cap on the number of stars the universe has made and will ever make? This question has long been a subject of intense astrophysical debate, particularly in relation to the stellar composition of individual galaxies. For example, our current cosmological paradigm (or at least the one that most scientists subscribe to) is that we live in a universe dominated by dark matter, and in a dark matter universe the biggest galaxies should have formed the most recently,4 being assembled by the hierarchical, gravitationally driven merger of smaller systems. Yet if you examine very large, massive galaxies you find that they tend to be composed of older stars, suggesting that they’ve already sat around in their dotage for a very long time.
To try to explain this, astronomers invoke the idea of “quenching,” where something acts to suppress or shut down the formation of new stars across galaxies.Caleb Scharf, “The Universe Has Made Almost All the Stars It Will Ever Make” at Nautilus
We live in a universe that, like it or not, has a beginning and an end. That is better suited to some philosophies than others.
Note: Caleb Scarf is also the author lf The Zoomable Universe: An Epic Tour Through Cosmic Scale, from Almost Everything to Nearly Nothing (2017):
The answer to life, the universe, and everything may actually be 63 – the number of orders of magnitude of physical scale that we can access.
The journey from the cosmic horizon to the subatomic is full of fascinating waypoints, but what do we really know about the nature of reality and what are the biggest mysteries still waiting to be solved?