Astronomers reveal explosive galaxy growth and declining star formation rates

New astronomical research is challenging established theories regarding how galaxies grow and how the universe produces stars.

Researchers from the Instituto de Astrofísica de Canarias (IAC) discovered that the spiral galaxy Messier 74 (M74) underwent an explosive growth period. Using data from the Transient Survey Telescope (TST), they identified a faint, blue outer disk of young stars that extends the galaxy to nearly 100,000 light-years from its center. This effectively doubles the known size of the galaxy, having occurred in less than one billion years, which is considered a very brief period in astronomical terms.

Separately, a study by the Chinese Academy of Sciences published in Nature Astronomy reveals that the cosmic star formation rate has dropped to less than half of what it was 4.5 billion years ago. Interestingly, this decline does not appear to be caused by a lack of raw materials. While the star formation rate has fallen by a factor of 2.46, the density of neutral hydrogen—the primary fuel for stars—has only decreased by a much smaller margin, suggesting that galaxies are not simply running out of gas.