As JWST pushes the limits, astronomers seem to discover galaxies with unusual, extreme, or peculiar properties, which question some of our previous knowledge or potentially even pose more fundamental problems e.g. to our standard cosmological model.
With this background, I will show recent evidence for unusual stellar populations (very massive stars, with masses >100 Msun) in compact star-forming galaxies at high-z (e.g. Upadhyaya et al. 2024). I will also present the properties of the so-called N-emitters discovered with JWST and discuss possible indications for the presence of supermassive stars (> 1000 Msun) in these very compact galaxies and their possible link with globular-cluster or super-massive black hole formation. Such extreme/unusual stars might be more common in the early Universe and therefore important to understand galaxies, star- formation and possibly also black-hole formation at very high-redshift.
