The universe still forms stars, but the average rate at which galaxies make them has fallen substantially from its cosmic peak. A widely cited peer-reviewed synthesis places that peak about 3.5 billion years after the Big Bang, roughly 10 billion years ago. The decline describes the rate of new star formation across the universe—not stars disappearing or every galaxy following the same history.
When did the universe stop making stars so quickly?
It did not stop. The cosmic star-formation-rate density—the rate at which galaxies collectively turn gas into stars per unit of comoving volume—rose early in cosmic history, reached a broad maximum, and declined afterward. In their 2014 review, astronomers Piero Madau and Mark Dickinson place the peak at about 3.5 billion years after the Big Bang, at redshift approximately 1.9. Their synthesis describes the post-peak decline with an e-folding timescale of 3.9 billion years. Read the review.
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An e-folding time is a way to describe exponential change: after one such interval, a fitted quantity would be about 37% of its starting value if that decline continued at the same rate. It is not a fixed annual percentage drop, nor does the fitted curve mean that each galaxy steadily lost star-forming activity in the same way.
Is the universe running out of stars?
No. The declining figure tracks how quickly new stars form, not how many stars already exist. Existing stars can continue shining for billions of years, and the total stellar population can grow even while its rate of growth slows.
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Madau and Dickinson estimated that half of the stellar mass observed today had formed before redshift 1.3. About a quarter formed before the cosmic star-formation peak, with another quarter forming after redshift 0.7. These figures describe when the accumulated stellar mass formed; they are not a count of stars lost or destroyed.
Why are fewer stars forming now?
Stars form from gas, and the cosmic rate reflects how much star-forming material galaxies have available and how efficiently they turn it into stars. The decline is a population-level pattern, not proof that every galaxy has run out of gas or that all galaxies faded together.
A recent, preliminary result offers another way to study that history. A University of British Columbia release about a 2025 Euclid–Herschel analysis of 2.6 million galaxies reports that average galactic dust temperatures were about 10 kelvins warmer ten billion years ago. The release says higher star-formation rates tend to occur in galaxies with hotter dust, but dust temperature is an indirect clue, not a direct count of newborn stars. The university described the associated paper as a preprint, so this result should be treated as preliminary rather than as a replacement for the established synthesis. Read the UBC release.
Douglas Scott, a University of British Columbia cosmologist and an author on the preprint, said: “The amount of dust in galaxies and their dust temperatures have been decreasing for billions of years, which means we’re past the epoch of maximum star formation.”
How do astronomers know what was happening billions of years ago?
Light takes time to travel. When astronomers observe distant galaxies, they see them as they were when the light left them, so surveys at different distances provide views of different cosmic epochs. Researchers combine observations across galaxies and wavelengths with theoretical tools to reconstruct the history of star formation and stellar-mass growth. The result is a history inferred from many galaxies, not a time-lapse recording of one galaxy changing over billions of years. Madau and Dickinson review the methods and their limits in their 2014 synthesis.
Older graphics can help explain how the picture developed, but they should not be mistaken for precise current measurements. NASA’s graph page, first released in 1996 and updated in 2025, describes a 12-billion-year history and notes that the original measurements left a gap around the peak. See NASA’s historical graph.
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What the Milky Way comparison does—and does not—show
NASA reported in 2015 that Milky Way-like galaxies formed stars at roughly 30 times today’s rate during their peak era, around 10 billion years ago. That is a comparison for galaxies similar in mass to the Milky Way, not a measurement of the universe-wide average. The estimate comes from examining deep-survey samples of similar-mass galaxies; astronomers cannot look at direct “baby pictures” of our own galaxy. Read NASA’s explanation.
The comparison makes the cosmic trend easier to picture, but individual galaxies have their own histories. A galaxy-specific rate and the combined rate density of all galaxies answer different questions.
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