Free Astronomy Magazine September-October 2025

45 SEPTEMBER-OCTOBER 2025 ASTRO PUBLISHING resolving the internal structures of these galaxies and learning about the processes happening within them.” The CRISTAL survey focused on a sample of star-forming galaxies that showed the typical relationship between a galaxy’s mass and its star formation rate. ALMA’s observations of these galaxies revealed: 1) Diverse Shapes and Motions: Some galaxies showed signs of orderly ro- tation, suggesting the formation of early disks. Others displayed chaotic motions and disturbed shapes, in- dicative of galaxies colliding and merging. 2) Extended Gas Clouds: ALMA de- tected clouds of gas, revealed by T his artist’s impression of the for- mation of an early universe gal- axy featuring clumps of star-forming galaxies, with carbon gas shown in red, and dark dust shown in black. This process is documented in detail throughout the many galaxies ob- served in ALMA’s CRISTAL survey. [NSF/AUI/NSF NRAO/B. Saxton] their emission of a specific type of light from ionized carbon, extending far beyond the regions where stars formed. This suggested that galaxies are surrounded by vast gas reser- voirs, potentially fueling future star formation or being expelled by pow- erful outflows. 3) Clumpy Star Formation: Many galaxies exhibited star formation oc- curring in distinct clumps, providing insights into how stars are born in these early systems. One particularly intriguing finding is the discovery of a galaxy, named CRISTAL-10, exhibiting an extreme deficit of ionized carbon emission relative to its far-infrared light, a ratio similar to that seen in Arp 220, one of the most luminous and ob- scured galaxies in the local Universe. Further study of this galaxy could re- veal the interstellar medium’s power source and physical state in the early Universe. “CRISTAL provides the kind of de- tailed data that simply wasn’t possi- ble before ALMA,” adds Herrera Camus, “We’ve got a new family portrait of early galaxy evolution. These observations are challenging our existing models of galaxy forma- tion and providing new avenues for research.” The CRISTAL survey demonstrates the power of ALMA for studying galaxy evolution in the early Uni- verse. By tracing the cold gas and dust that fuel star formation, ALMA is helping scientists piece together the story of how galaxies like our own Milky Way came to be. !