A supernova rara revela a anatomia oculta de uma estrela ao se romper
On September 6, 2021, Steve Schulze, a researcher at Northwestern University, was searching for new supernovae when he came across a strange explosion that left behind a very exposed corpse. The star suffered a violent death that shattered it to expose its inner layers. “We immediately noticed that this supernova was unlike anything we had seen before,” Schulze told Gizmodo.
When massive stars approach their death, they develop layers or shields composed of different elements. These layers are difficult to observe because the star’s explosive death mixes them. But for the first time, astronomers have been able to see the defined layers that form a star, thanks to a newly discovered supernova called 2021yfj. It is nothing like what they expected. The discovery is detailed in a new article in Nature, challenging existing models of stellar life cycles and the processes leading to explosive death.
### What the supernova 2021yfj revealed
When stars are born, they are bright balls of hydrogen. Due to the pressure and temperature of the star’s core, hydrogen fuses to form helium and then turns into carbon, leading to the formation of iron in the core. “This transforms the star into a layered structure,” Schulze said. A layer rich in oxygen, silicon, and sulfur is buried beneath many other materials and forms just months before the star explodes, making direct observation impossible. Until now.
At the Zwicky Facilities in San Diego, California, the supernova 2021yfj was discovered while monitoring the night skies every two or three days. After the initial observations, the researchers of this discovery worked to identify the mysterious features of its spectrum and found that silicon, sulfur, and argon were producing them. They also detected traces of helium in the supernova’s spectrum. “Any helium that would have been present would have been consumed in earlier fusion stages, so detecting helium in the spectrum of SN 2021yfj is intriguing to us,” Schulze said.
Observations of a star down to its oxygen and silicon-rich layers indicate an extremely rare stripping process that can occur due to strong stellar winds, eruptions, or interactions with a companion star, according to researchers.
“This is the first time we have observed the shields or layers of the interior of a massive star, something significant to test and improve our models of stellar evolution,” Schulze said. “Observations of stripped stars and supernovae are essential for improving and validating models of stellar evolution.” “SN 2021yfj reveals that we still have not finished understanding how massive stars evolve and how their lives end,” added the researcher.
