Astronomers have captured one of the rarest moments in the world of astrophysics, the initial phase of a supernova explosion. On April 10, 2024, the Asteroid Terrestrial-impact Last Alert System (ATLAS) system first detected the initial light from the explosion of a massive star whose mass is estimated to be 12-15 times greater than the Sun. Just 26 hours later, a team of astronomers aimed the Very Large Telescope (VLT) in Chile at the site of the explosion to study the early stages of the star’s death.
This explosion was named SN 2024ggi and occurred in the galaxy NGC 3621, which is about 22 million light years away in the constellation Hydra. This image from VLT observations taken on April 11, 2024 shows the position of the supernova in the galaxy.
Supernovas occur when a star’s balance is disturbed. Massive stars maintain almost perfect shape due to the inward gravitational pull and radiation pressure from nuclear fusion reactions in the core pushing outward. When this pressure is no longer able to withstand gravity, the star’s core collapses. The star’s outer layers are then sucked inward before bouncing back, creating a powerful shock wave that explodes the star.
When the shock wave penetrates the surface of the star, so much energy is released that the supernova suddenly becomes very bright. However, how these shock waves form and move outward is still one of the big questions in supernova studies.
There is a short window of time after the explosion occurs, which allows astronomers to see the initial “breakout” form of the explosion. Through spectropolarimetry techniques, which separate light based on its wavelength and direction of vibration, VLT scientists managed to capture this initial form for the first time.
Data from the FORS2 instrument, the only facility in the Southern Hemisphere capable of making such measurements, shows that the initial light from the supernova was not radiated evenly in all directions. The shape of the shock wave extends along one axis, resembling an olive. This shows that the explosion is not perfectly round.
Around day 10, the hydrogen-rich outer layers of the star begin to become visible. This layer has the same orientation as the shape of the first day’s shock wave, indicating that the direction of the explosion was stable from the start.
This rare observation helps refine a number of existing supernova models and supports other theories. As well as providing new insight into the process of destruction of massive stars. (Live Science/Z-2)
