Supernovae are among the most energetic phenomena in the Universe, and definitely one of the most spectacular! These events take place when a star has reached the end of its life cycle and undergoes gravitational collapse at its center, exploding and shedding its outer layers in the process. For astronomers, supernovae are not only a fascinating field of study, shedding light on the evolution of stars, but are also a means of measuring distance and the rate at which the Universe is expanding. They are an essential part of the Cosmic Distance Ladder because their brightness makes them very reliable “standard candles.”

Spotting supernovae represented a major challenge, though, since they are transient events that are extremely difficult to predict. Luckily, astronomers are getting better at spotting supernovae thanks to high-cadence surveys by observatories that continuously monitor the skies. According to a new study led by the Institute of Space Sciences (ICE-CSIC) in Barcelona, it is still crucial to develop protocols and methods for detecting them promptly. They further present a methodology for obtaining the spectra of supernovae as soon as possible by combining wide-field sky surveys with immediate follow-up by telescopes.

The research was led by Lluís Galbany, a staff researcher at the Institute of Space Sciences (ICE-CSIC) and a member of the Institut d’Estudis Espacials de Catalunya(IEEC). He and his colleagues at the ICE-SCIC and IEEC were joined by researchers from the European Southern Observatory (ESO), the Institut de Física d’Altes Energies (IFAE), the Instituto de Ciencias Exactas y Naturales (ICEN), the Instituto de Astrofísica de La Plata (IALP), and numerous universities worldwide. Their paper, “Rapid follow-up observations of infant supernovae with the Gran Telescopio Canarias,” has been published in the Journal of Cosmology and Astroparticle Physics (JCAP).

Artistic elaboration based on images from the original paper Galbany et al., JCAP, 2025. Credit: Galbany et al., JCAP, 2025

Detecting a supernova during the first hours and days after it explodes is essential since the explosion preserves direct clues about the progenitor system. This information helps distinguish between competing explosion models and allows astronomers to estimate critical parameters and study the local environment. This has proved very challenging in the past because most supernovae were detected days or weeks after the explosion event. These explosions fall into two broad categories, which are determined by the mass of the progenitor star.

The first are known as thermonuclear supernovae, which involve stars whose initial mass did not exceed eight Solar masses (typically white dwarfs). If these stars are part of a binary system, their powerful gravity will likely siphon material from their companion, raising the star’s internal pressure until it explodes in a Type Ia supernova. The second type is core-collapse supernovae, which involve massive stars whose initial mass exceeds this limit. As Galbany summarized in an ICE-CSIC press release:

They shine thanks to nuclear fusion in their cores, but once the star has burned through progressively heavier atoms—right up to the point where further fusion no longer yields energy—the core collapses. At that point, the star collapses because gravity is no longer counterbalanced; the rapid contraction raises the internal pressure dramatically and triggers the explosion. The sooner we see them, the better.

As noted, high-cadence surveys that cover large sections of the sky and revisit them frequently are changing this, though protocols are still needed to exploit the data they collect. The protocol developed by Galbany and his colleagues begins with a rapid search for candidates based on the criteria that it was absent in the previous night’s images, and the new light source lies within a galaxy. When both conditions are met, the team triggers the Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) instrument on the Gran Telescopio de Canarias (GTC) to obtain spectra from the explosions. Said Galbany:

The supernova’s spectrum tells us, for instance, whether the star contained hydrogen—meaning we are looking at a core-collapse supernova. Knowing about the supernova in its very earliest moments also lets us seek other kinds of data on the same object, such as photometry from the Zwicky Transient Facility (ZTF) and the Asteroid Terrestrial-impact Last Alert System (ATLAS) that we used in the study. Those light-curves show how brightness rises in the initial phase; if we see small bumps, it may mean another star in a binary system was swallowed by the explosion.

The ICE Gran Telescopio Canarias telescope, located at the El Roque de los Muchachos Observatory on the island of La Palma, Spain. Credit: Instituto de Astrofísica de Canarias

The team tested this method using GTC data and found ten supernovae that occurred within six days, two within the first 48 hours. The ten events were divided equally into the thermonuclear and core-collapse categories, and the team confirmed them by making additional cross-matches with data obtained by other observatories on the same patch of sky. Based on the success of their study, the team believes that even faster detections are within reach. As Galbany summarized:

What we have just published is a pilot study. We now know that a rapid-response spectroscopic program, well coordinated with deep photometric surveys, can realistically collect spectra within a day of the explosion, paving the way for systematic studies of the very earliest phases in forthcoming large surveys such as the La Silla Southern Supernova Survey (LS4) and the Legacy Survey of Space and Time (LSST), both in Chile.

Further Reading: ICE-CSIC, arXiv

Less than four years into his tenure, Santa Monica’s first-ever Latino police chief, Ramón Batista, has announced his resignation from a department in which he oversaw a drop in crime and increased police hiring.

Batista hinted at a potential clash with city leaders in a letter on Friday to the city manager, Oliver Chi.

“My nearly 40 years of experience in public safety and policing, my deeply held sense of justice, and following not only the spirit, but the letter of the law, appear to be at odds from demands set by the new administration,” he wrote.

“In that light, the right path is to transition leadership here, as I look forward with purpose, conviction, and optimism to my next challenge.”

Batista said in his letter that his last day would be Oct. 4, exactly two weeks before his fourth anniversary of being sworn in as Santa Monica’s 18th police chief over its 128 years.

Batista and Santa Monica officials did not immediately respond to requests for comment.

Chi, who received Batista’s letter, said in a statement he was grateful for the chief’s “many contributions.”

“His dedication, kindness and vision have shaped our police department in positive ways, and on behalf of the entire organization, we honor and thank him for his service,” Chi said.

The city manager also noted that Santa Monica Deputy Chief Darrick Jacob would serve as acting police chief.

Chi said Jacob had served the department for more than 20 years, with responsibilities including overseeing daily operations.

“I am supremely confident that our staff, the police department, and the entire community will be well served by Acting Chief Jacob,” Chi said.

Chi did not lay out a process or a timeline for finding a permanent replacement.

A call to the Santa Monica Police Officers Assn., which endorsed Batista’s hiring, was not returned.

Batista claims a few victories in his resignation letter, including helping rebuild morale after Santa Monica endured a chaotic protest in May 2020 in which hundreds were arrested in the wake of the death of George Floyd.

In May 2021, an outside analyst hired by the city found several shortcomings in the department’s reaction to the protest. Although no one died, the OIR Group found that widespread “vandalism and property damage, the losses to business and the divisive handling of protesters” ultimately undermined the “confidence in people’s basic security.”

OIR made 44 recommendations to the city, including addressing the department’s high turnover rate and not relying on overtime as a fix for low staffing. The report also criticized a lack of planning in the lead-up to the protest.

“During that period, morale was low, many officers were sidelined due to injuries, and the department was stretched thin,” he wrote.

Batista said in his letter that the department had 177 working police officers when he took over in October 2021. He said that number had been bumped up to 231.

Part of what made Batista an attractive prospect for Santa Monica in the summer of 2021 was his ability to fight crime.

By the end of his 2½-year run as the police chief of Mesa, Ariz., his department had lowered Part I crimes to a city all-time low of 23 events per 1,000 residents.

Part I crimes, according to the FBI’s Uniform Crime Reporting Program, refer to eight specific categories of serious offenses: criminal homicide (murder and non-negligent manslaughter), rape, robbery, aggravated assault, burglary, larceny-theft, motor vehicle theft and arson.

In 2024, the department recorded 50,000 proactive contacts with residents and businesses while responding to 128,000 service calls, according to Batista.

He said his department made 2,800 arrests, which led to a 2% reduction in Part I crimes.

“I leave confident that the department is stronger, more modern, and more connected to the community than when I arrived,” he said.