Supernovae are sudden stellar explosions that flare brightly in the sky, making them difficult to capture in their earliest moments. With modern wide-field, high-cadence sky surveys, astronomers can now spot these events almost daily, but protocols are needed to secure immediate follow-up data.
A pilot study led by Lluis Galbany of the Institute of Space Sciences (ICE-CSIC) in Barcelona te by Erica Marchand
Paris, France (SPX) Aug 20, 2025
Supernovae are sudden stellar explosions that flare brightly in the sky, making them difficult to capture in their earliest moments. With modern wide-field, high-cadence sky surveys, astronomers can now spot these events almost daily, but protocols are needed to secure immediate follow-up data.
A pilot study led by Lluis Galbany of the Institute of Space Sciences (ICE-CSIC) in Barcelona tested a methodology to obtain supernova spectra within 48 hours-or even 24 hours-of first light. The team applied the method at the Gran Telescopio de Canarias (GTC), observing ten supernovae: five thermonuclear and five core-collapse, with two detected within two days of explosion.
Thermonuclear supernovae occur when white dwarfs in binary systems accumulate matter until reaching critical mass, while core-collapse supernovae arise from massive stars above eight solar masses exhausting their nuclear fuel. In both cases, the earliest spectra reveal crucial details of the progenitor system, explosion mechanics, and local environment.
The team's protocol relies on identifying new light sources absent from the previous night's images and located within galaxies. Once a candidate is confirmed, they trigger the GTC's OSIRIS instrument for rapid spectroscopy. Cross-referenced photometry from Zwicky Transient Facility (ZTF) and Asteroid Terrestrial-impact Last Alert System (ATLAS) further clarifies light-curve evolution.
"The supernova's spectrum tells us, for instance, whether the star contained hydrogen-meaning we are looking at a core-collapse supernova," Galbany said. Early light-curves can also indicate binary interactions, with small bumps in brightness signaling a companion star consumed by the blast.
This study demonstrates that rapid-response spectroscopy can realistically be achieved within a day, positioning astronomers to exploit future large surveys such as Chile's La Silla Southern Supernova Survey (LS4) and the Legacy Survey of Space and Time (LSST).
Research Report:Supernovae: How to spot them at record speed
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