On December 12, 2024, an international team of astronomers announced the detection of an exceptionally rapid and bright cosmic explosion, designated CSS161010, originating from a small galaxy located 500 million light-years away.
This event reached its peak brightness within just four days and diminished to half its luminosity in 2.5 days, marking a significant scientific milestone and presenting challenges for the research team. The findings were published in The Astrophysical Journal.
CSS161010 was first identified by the Catalina Real-Time Transient Survey, with prior detection noted by the All-Sky Automated Survey for SuperNovae. Follow-up observations were conducted using the Gran Telescopio Canarias (GTC) and the Nordic Optical Telescope (NOT) at the Roque de Los Muchachos Observatory, operated by the Instituto de Astrofísica de Canarias (IAC).
Rapidly evolving cosmic phenomena have historically been difficult to study due to their nature. However, advancements in modern techniques and instrumentation have enhanced field of view and high-resolution imaging capabilities.
Only a handful of cosmic explosions with similar brightness and evolution have been detected, with their origins remaining largely unknown. The research team, led by Claudia Gutiérrez, posits that the unique spectral properties of CSS161010 provide crucial insights into its physical origin, suggesting it may result from a small black hole consuming a star.
This conclusion was drawn from the observation of broad hydrogen lines exhibiting velocities of up to 10% of the speed of light, alongside unprecedented evolution. Two months post-explosion, the brightness of the object had decreased 900 times from its peak.
Surprisingly, spectra captured by the GTC revealed that all hydrogen line profiles remained blue-shifted, indicating extreme velocities toward Earth. This suggests a strong gas outflow, an unexpected finding for a supernova.
Claudia Gutiérrez, the study's lead author and postdoctoral researcher at the Institute of Space Studies of Catalonia (IEEC) and the Institute of Space Sciences (ICE-CSIC), stated, "Discovering and analyzing these cosmic explosions is particularly challenging due to their rapid evolution. However, our collaboration's swift response allowed us to obtain high-quality spectra, revealing unique properties never before observed, enabling us to clarify the nature of this extraordinary event."
She further remarked, "When we saw the spectra, we were at a loss for words. We had never encountered such a blue-shifted hydrogen line profile; this shift indicated that the gas is moving toward us at extremely high speeds. This feature was both surprising and intriguing, prompting us to investigate possible connections with the galaxy where the event occurred."
The explosion took place in a diminutive galaxy with a stellar mass approximately 400 times less than that of the Milky Way. Consequently, if the galaxy harbors a massive black hole, its mass must also be relatively small, corresponding to an intermediate-mass black hole (100-100,000 solar masses).
Professor Seppo Mattila from the University of Turku in Finland, a co-author of the study, noted, "To date, such black holes have been extremely difficult to identify, with astronomers aware of only a very limited number of confirmed cases."