FAST Telescope Uncovers Why Star Formation Slows Despite Abundant Hydrogen
Using the FAST radio telescope and DESI, researchers analyzed ~2.5 million galaxies over 4.5 billion years to track neutral hydrogen. They found that 4.5 billion years ago the cosmic star-formation rate was about 2.5 times higher than today, while neutral hydrogen density was only ~1.4 times higher, indicating gas reserves did not simply deplete as star formation declined. The study suggests that as the overall gas density falls, the efficiency of converting neutral hydrogen to molecular gas (the fuel for stars) decreases, shrinking the molecular reservoir and slowing star formation. Findings published in Nature Astronomy.
