Frist Light on Stellar Demise: Astronomers Capture Earliest Moments of a Supernova
astronomers have, for the first time, directly observed the initial shape of a massive star as it exploded in a supernova. The event, designated SN 2024ggi, was detected in April 2024 adn rapidly targeted by the European Southern Observatory’s (ESO) Very Large Telescope (VLT) in Chile just 26 hours later.This swift response allowed researchers to capture the supernova in its earliest stages – precisely as the energetic blast wave ruptured the star’s surface.
Supernovas represent the dramatic end-of-life for stars significantly larger than our sun. Understanding the geometry of these explosions is crucial for unraveling the complexities of stellar evolution and the underlying physics driving these cosmic events, according to Yi Yang, an astronomer at Tsinghua University and co-author of a study detailing the findings, published in Science Advances.
The death of massive stars (those exceeding eight times the sun’s mass) remains a subject of ongoing research. Current theory suggests that when a star exhausts its fuel, its core collapses, causing surrounding material to fall inward before rebounding in a shockwave.This shockwave then propagates outward, releasing immense energy upon breaching the star’s surface and creating the visible supernova. Though, the precise mechanisms initiating and driving this shockwave have been a long-standing puzzle.
SN 2024ggi occurred within the NGC 3621 galaxy, located 22 million light-years from earth. Prior to its explosion, the star was a red supergiant, estimated to be 12 to 15 times the mass of the Sun and possessing a radius 500 times larger.
The research team utilized a technique called spectropolarimetry to capture the fleeting “breakout” shape – the initial form of the explosion before it interacted with surrounding interstellar material. Lifan Wang, a co-author from Texas A&M University, explained that spectropolarimetry provides unique information about the explosion’s geometry, unavailable through other observational methods.
While the observation doesn’t yield a traditional, colorful photograph of the explosion (the image accompanying this report is an artist’s interpretation based on the data), the researchers were able to reconstruct the supernova’s shape by analyzing the polarization of its light. Polarization, a property of light waves, can reveal details about the shape of the emitting object.
The analysis revealed that the initial blast wave was distinctly olive-shaped. As the ejected material expanded and collided with surrounding matter, it flattened, but crucially, maintained the same axis of symmetry. Yang stated that these findings point towards a consistent physical mechanism driving the explosions of many massive stars, characterized by a defined axial symmetry operating on a large scale.
this groundbreaking observation allows astronomers to refine existing supernova models, discarding those inconsistent with the observed olive shape and improving those that align with the new data.The findings represent a significant step forward in understanding the powerful and complex processes that govern the deaths of massive stars.
