The anticipation of five long years finally paid off the day before my thesis examination when my friend and radio astronomer, Joe Callingham, shared an image with me. It was an infrared photo of two dying stars captured by the Very Large Telescope in Chile. The stars were enveloped in a massive spiral of dust, resembling a serpent consuming its own tail. We named this celestial phenomenon “Apep” after the Egyptian serpent god of destruction.
Recently, our team had the privilege of using NASA’s James Webb Space Telescope (JWST) to observe Apep in even more detail. The new image, analyzed in two papers on arXiv, revealed a breathtaking view of the dying stars. These stars, known as Wolf-Rayet stars, undergo a violent process before turning into supernovae. They shed their outer hydrogen layers, exposing their heavy cores, and their powerful winds clash with those of their companion stars, creating a unique environment where dust can condense.
Contrary to our expectations, Apep turned out to be not just one, but two Wolf-Rayet stars with equally strong winds. The dust surrounding them forms a wide cone-like shape, unlike the typical spiral nebula we anticipated. The JWST’s infrared camera provided a new perspective on Apep, showcasing the hot material in blue and the cooler material in green to red hues.
The detailed data from JWST revealed three additional dust shells surrounding Apep, each cooler and fainter than the last. This information, published in two papers led by Yinuo Han and Ryan White, provided insights into the cooling of the nebula’s dust, the stars’ distance from Earth, and the precise orbit of the inner stars. It also confirmed the existence of a third star in the Apep system.
Studying systems like Apep not only enhances our understanding of star deaths and the creation of carbon dust but also reveals the beauty and complexity of the universe. The intricate geometry and violent processes of stellar deaths present scientific puzzles that continue to intrigue researchers. Solving these mysteries is not only a scientific endeavor but also a source of joy and wonder.
As an Associate Professor at Macquarie University, I find immense satisfaction in unraveling the mysteries of the cosmos and sharing them with the world. The beauty and complexity of celestial phenomena like Apep remind us of the wonders of the universe and the endless possibilities for discovery.
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