Declining star formation not caused by simple 'fuel crisis,' new measurements suggest
The universe has been having fewer and fewer stellar "babies." Over the past 4.5 billion years, the rate of star birth has crashed to less than half of what it once was. But here's the twist: the most essential "fuel" for making stars has barely decreased.
Recent measurements indicate that the universe's declining star formation is not due to a simple fuel crisis. The rate of stellar birth over the past 4.5 billion years has dropped to less than half of its former levels. However, the essential fuel for star creation—cosmic neutral atomic hydrogen—has only slightly decreased. This surprising finding comes from an international team led by researchers from the Chinese Academy of Sciences and the Dark Energy Spectroscopic Instrument.
Using China's Five-hundred-meter Aperture Spherical radio Telescope, the team measured high-precision cosmic neutral atomic hydrogen over the past 4.5 billion years. The study, published in Nature Astronomy, shows that despite the dramatic decline in star formation, neutral atomic hydrogen has only marginally decreased. This discovery challenges the notion that the universe's gas is simply running out.
Instead, it suggests that the difficulty in forming stars may stem from less efficient conversion of atomic hydrogen into molecular gas, the primary fuel for star formation. The research establishes a new benchmark for understanding the late-stage cosmic gas cycle and the broader evolution of galaxies.
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