As scientists excitedly await the first light of the Vera C. Rubin Observatory, a recent study has projected that this facility will aid in identifying hundreds of massive stars on the cusp of death.
Before Detonation
Throughout their lifetimes, stars burn through hydrogen in their cores — million-degree furnaces smashing atoms together to form new ones. Massive stars, many times the mass of our Sun, have very high temperatures and pressures in their cores, causing them to live fast and die young. When all the fuel is burned, the star no longer produces enough thermal pressure to balance gravity, and the star dies in a rapid and massive explosion known as a Type II (or core-collapse) supernova.
But the final stages of a massive star’s life are not yet fully understood. Observations of Type II supernovae show narrow emission lines that indicate that their progenitor stars were surrounded by circumstellar material — material that was shed from the star as it evolved. However, the exact mechanism through which these stars lose mass is unclear, but if we can catch a star nearing its end but before its deadly detonation, we can better understand these massive stars’ elusive final days.
But the final stages of a massive star’s life are not yet fully understood. Observations of Type II supernovae show narrow emission lines that indicate that their progenitor stars were surrounded by circumstellar material — material that was shed from the star as it evolved. However, the exact mechanism through which these stars lose mass is unclear, but if we can catch a star nearing its end but before its deadly detonation, we can better understand these massive stars’ elusive final days.
Rubin’s Remedy
Looking to explore many facets of the universe, the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST), first light anticipated July 2025, will scan the Southern Hemisphere sky searching for transient events like supernovae. Recognizing the power of LSST, Alexander Gagliano (The NSF AI Institute for Artificial Intelligence and Fundamental Interactions) and collaborators run simulated observations to predict how many stars LSST will catch in their final days, before they explode as supernovae.
Previous observations of Type II supernovae reveal enhanced emission in the months to years prior to explosion, and as LSST monitors the sky, it will be able to capture this pre-explosion emission. The authors carefully model the expected light curves for various types of core-collapse supernova precursors based on the handful of pre-explosion emission events observed thus far. With these models, the authors simulate LSST observations, applying two methods that would allow for the detection of stars gearing up to explode. The first being single-visit observations in which the enhanced emission is detected using differential photometry prior to the star’s explosion, independent of detecting the subsequent supernova. The second method involves going back after a supernova has been detected. By performing binned photometry of the star with observations taken of it prior to its explosion, the preceding emission can be recovered. From here, the authors can predict how many events LSST will recover after it goes online.
Previous observations of Type II supernovae reveal enhanced emission in the months to years prior to explosion, and as LSST monitors the sky, it will be able to capture this pre-explosion emission. The authors carefully model the expected light curves for various types of core-collapse supernova precursors based on the handful of pre-explosion emission events observed thus far. With these models, the authors simulate LSST observations, applying two methods that would allow for the detection of stars gearing up to explode. The first being single-visit observations in which the enhanced emission is detected using differential photometry prior to the star’s explosion, independent of detecting the subsequent supernova. The second method involves going back after a supernova has been detected. By performing binned photometry of the star with observations taken of it prior to its explosion, the preceding emission can be recovered. From here, the authors can predict how many events LSST will recover after it goes online.
Power in Numbers
Based on their analysis, the authors predict that LSST will detect ~150–240 Type II supernova progenitors per year with single-visit photometry. Over the course of the first three years of LSST, they anticipate 150–400 detections from the binned photometry. This projected frequency of detections will launch the study of late-stage stellar life to new levels, increasing the observed sample of Type II supernova progenitors astronomically. As these detections come in, the observations will reveal the properties and behaviors of these stars in their final days. This opens the door to understanding how end-stage massive stars lose mass and ignite into the most powerful events in the universe.
By Lexi Gault
Citation
“Finding the Fuse: Prospects for the Detection and Characterization of Hydrogen-rich Core-collapse Supernova Precursor Emission with the LSST,” A. Gagliano et al 2025 ApJ 978 110. doi:10.3847/1538-4357/ad9748
