An international team of scientists, led by Dr. Claudia Gutiérrez from the Institute of Space Studies of Catalonia (IEEC) and the Institute of Space Sciences (ICE-CSIC), has made an extraordinary discovery: an exceptionally fast and bright cosmic explosion in a small galaxy 500 million light-years away. This remarkable event, designated CSS161010, has been documented in The Astrophysical Journal and has provided unprecedented insights into the mechanisms behind such rare phenomena.
CSS161010 reached peak brightness in just four days, then dimmed to half its maximum in a mere 2.5 days. This rapid evolution posed a significant challenge for the researchers, who had to act quickly to observe and analyze the event. The discovery was initially made through the Catalina Real-Time Transient Survey, and earlier observations were recorded by the All-Sky Automated Survey for SuperNovae (ASAS-SN). The subsequent follow-up involved telescopes at the Roque de los Muchachos Observatory in La Palma, specifically the Gran Telescopio Canarias (GTC) and the Nordic Optical Telescope (NOT), managed by the Instituto de Astrofísica de Canarias (IAC). These high-resolution instruments allowed the researchers to capture crucial data and track the explosion’s evolution.
Rapidly evolving cosmic events like CSS161010 are notoriously difficult to study because they fade quickly and are rare by nature. Until now, only about a dozen similar events have been observed, leaving their origins shrouded in mystery. However, the unique properties of CSS161010 have provided the research team with critical clues, leading to a groundbreaking hypothesis: the event was caused by a small black hole swallowing a star.
The defining features of CSS161010 include its broad hydrogen lines, which indicated gas moving at speeds up to 10% of the speed of light, and its unprecedented brightness drop—decreasing by a factor of 900 in just two months. Notably, even after the brightness had significantly faded, the hydrogen lines captured by the GTC remained blueshifted, suggesting a strong outflow of gas moving toward Earth at immense speeds. Such behavior is highly unusual and not typically associated with supernovae, pointing instead to a more exotic origin.
Dr. Gutiérrez emphasized the significance of this discovery, noting that the rapid evolution and unique spectral characteristics of CSS161010 made it unlike any previously observed object. “The data revealed properties we had never seen before, allowing us to narrow down the nature of this extraordinary event,” she explained. The team’s analysis suggests that the explosion resulted from a process called a tidal disruption event, where a star gets too close to a black hole and is torn apart by its immense gravitational forces.
This particular tidal disruption event occurred in a dwarf galaxy, a galaxy much smaller and less massive than our Milky Way. The host galaxy’s small size implies that its central black hole is not supermassive but rather belongs to a category known as intermediate-mass black holes (IMBHs). These black holes have masses ranging from 100 to 100,000 times that of the Sun and are thought to represent a transitional stage in the growth of supermassive black holes, which dominate the centers of large galaxies.
Intermediate-mass black holes are notoriously difficult to detect. Unlike supermassive black holes, which are often active and surrounded by glowing accretion disks, IMBHs are usually quiescent, making them nearly invisible. Events like CSS161010 offer a rare opportunity to study these elusive objects. According to Professor Seppo Mattila of the University of Turku, identifying and characterizing IMBHs is crucial for understanding black hole formation and the evolutionary pathways that lead to the creation of supermassive black holes. Such insights could also shed light on how these massive objects formed in the early universe.
Professor Peter Lundqvist of Stockholm University added that the emission lines observed in CSS161010 share similarities with those seen in active galactic nuclei, where supermassive black holes reside. This resemblance strengthens the case that CSS161010’s host galaxy contains an IMBH. “The disruption of a star by the black hole makes its presence visible, providing a rare glimpse into a type of black hole that would otherwise remain hidden,” he said.
The discovery of CSS161010 highlights the importance of cutting-edge observational technology in modern astrophysics. Telescopes with wide fields of view and high observational cadences, such as those used in this study, are essential for capturing and characterizing these transient cosmic phenomena. As Dr. Gutiérrez explained, “Telescopes that scan the sky frequently will be key to finding more of these rare and rapidly evolving events. Ground-based spectrographs, like those at the Roque de los Muchachos Observatory, will continue to play a pivotal role in understanding their nature.”
This breakthrough marks a significant step forward in the quest to unravel the mysteries of intermediate-mass black holes and the cosmic phenomena they produce. By combining advanced observational techniques with international collaboration, researchers are uncovering new windows into the universe’s most enigmatic processes. Events like CSS161010 not only deepen our understanding of black hole dynamics but also provide invaluable insights into the complex interplay between galaxies and the compact objects they harbor. As technology continues to advance, the era of discovering and studying these fleeting yet profound cosmic explosions is only just beginning.