NASA’s James Webb Space Telescope’s mid-infrared image shows four coiled shells of dust around a pair of Wolf-Rayet stars known as Apep for the first time.
Image: NASA, ESA, CSA, STScI; A.
NASA’s James Webb Space Telescope has captured a remarkable new image of Apep, a rare triple star system where shells of dust are expanding outward in spectacular fashion.
About 8,000 light-years away in the Southern Hemisphere constellation Norma, Apep is named after the ancient Egyptian serpent god of chaos. The messy star system comprises stars orbiting each other and a third, more massive supergiant star, orbiting them both.
‘Wolf’ Stars Explained
It gets weirder. The two stars orbiting each other are Wolf-Rayet stars, an unusual type of massive, dying star that can explode violently as a supernova as it reaches the end of its life. Only about 1,000 Wolf-Rayet stars have been found in the Milky Way — and Apep is the only known example containing two Wolf-Rayet stars of this type.
These two have been pushing out rings of dust for about 700 years, but until now they’ve mostly gone unseen. Ground-based telescopes have imaged Apep before, but have revealed only a single dust shell. JWST’s latest image reveals three, with a fourth, almost transparent shell detectable at the edge of the image.
‘One-Of-A-Kind’ Star System
What you see in the image is what the dust structures produced when two closely orbiting Wolf-Rayet stars approach each other, their strong stellar winds colliding. Researchers determined that the stars complete an orbit around each other every 190 years, forming new dust during their close encounters over the course of 25 years. “This is a one-of-a-kind system with an incredibly rare orbital period,” said Ryan White, a PhD student at Macquarie University in Sydney, Australia, and lead author on a paper published this week in The Astrophysical Journal. “The next longest orbit for a dusty Wolf-Rayet binary is about 30 years,” he added. “Most have orbits between two and 10 years.”
Faint Infrared Light
The new image combines JWST’s data with that from the European Southern Observatory’s Very Large Telescope in Chile, but it’s JWST’s ability to detect faint infrared light emitted by warm carbon dust that allowed scientists to see the extra spirals.
Webb’s data also revealed that Apep is a triple-star system. A third star, a massive supergiant, orbits at a greater distance and distorts the dust shells, carving a visible V-shaped gap from about 10 o’clock to 2 o’clock in the image. “The cavity is more or less in the same place in each shell and looks like a funnel,” said White.
What’s Next for Apep
The future of the Apep system is violent and uncertain. Both Wolf-Rayet stars are shedding mass rapidly and are expected to end their lives in supernova explosions. Either may produce a gamma-ray burst — one of the most energetic events in the universe — and eventually collapse into black holes.
“Looking at Webb’s new observations was like walking into a dark room and switching on the light — everything came into view,” said Yinuo Han, a postdoctoral researcher at Caltech in Pasadena, California, and lead author of a second paper published this week about the image.
This is not the first time JWST has been pointed at a Wolf-Rayet star. In March 2023, NASA published a stunning image of WR 124 about 15,000 light-years distant.
Wishing you clear skies and wide eyes.
