Diverse Type IIn Supernova Environments Revealed by Hubble Imaging at Z < 0.02

Type IIn supernovae, powerful explosions characterised by bright hydrogen emission, continue to puzzle astronomers regarding the origins of the stars that create them and the reasons for their substantial pre-explosion mass loss. Zexi Niu, Ning-Chen Sun, and Emmanouil Zapartas, from the University of Chinese Academy of Sciences and the Foundation for Research and Technology-Hellas respectively, alongside Conor L. Ransome, Justyn R. Maund, and Cesar Rojas-Bravo et al., have now undertaken a detailed investigation into the environments surrounding these supernovae to shed light on this mystery. Their research, utilising high-resolution images from the Hubble Space Telescope, analyses the local stellar neighbourhoods of 31 Type IIn supernovae within a relatively close distance to Earth. The team discovered a surprising diversity in these environments, categorising them into regions actively forming stars, those outside such regions, and older areas devoid of recent star birth. This variation, coupled with a clear link between supernova brightness and environmental type, suggests that Type IIn supernovae arise from a far wider range of stellar masses and evolutionary histories than previously thought.

These environments were then classified into three distinct types: Class 1, residing within star-forming regions; Class 2, located outside such regions; and Class 3, found in older environments devoid of obvious star formation.

This classification scheme allowed the team to correlate the environments with the intrinsic luminosity of the supernovae. The research team utilized high-resolution Hubble Space Telescope (HST) imaging to categorize the supernovae into three distinct classes based on their environments: Class 1 residing within star-forming regions, Class 2 outside star-forming regions, and Class 3 in older environments devoid of recent star formation.

This work establishes a clear link between the surrounding environment and the intrinsic properties of the supernovae, offering new insights into the progenitors of these energetic events. Experiments revealed a strong correlation between supernova brightness and environmental class. The study categorises these environments into three classes , those within active star-forming regions, those outside such regions, and those in older environments devoid of recent star formation , and demonstrates a clear correlation between supernova luminosity and environmental class.

Brighter supernovae tend to originate in star-forming regions, while fainter events are found in more isolated settings, suggesting a range of progenitor masses and evolutionary histories. Furthermore, the investigation indicates that directly observed supernova progenitors are often brighter and bluer than the surrounding stellar populations.