By utilizing data from the NASA/ESA/CSA James Webb Space Telescope along with ESO’s Very Large Telescope (VLT), two separate teams of astronomers have captured mid-infrared images of a system featuring four intricate spirals of dust encircling a pair of aging Wolf-Rayet stars located in a system known as Apep (2XMM J160050.7-514245).
Webb’s mid-infrared images reveal four coiled dust shells surrounding two Wolf-Rayet stars known as Apep. Image credits: NASA / ESA / CSA / STScI / California Institute of Technology Yeahuo Han / Macquarie University Ryan White / Alyssa Pagan, STScI.
Wolf-Rayet stars represent a rare class of massive binary stars where the universe’s earliest carbon is formed.
There are estimated to be only around 1,000 of these stars in the Milky Way galaxy, which contains hundreds of billions of stars in total.
Among the multiple Wolf-Rayet binaries observed so far, the Apep system stands out as the sole example of having two such Wolf-Rayet stars within our galaxy.
In a recent study, astronomer Ryan White from Macquarie University and his team set out to refine the orbital characteristics of the Wolf-Rayet stars in the Apep system.
They integrated precise ring position measurements from the Webb images with the shell’s expansion rate obtained over eight years of VLT observations.
“This is a unique system with a very extended orbital period,” White mentioned.
“The next longest orbit for a dusty Wolf-Rayet binary is roughly 30 years, while most orbits tend to span between 2 and 10 years.”
One of the team’s papers was published concurrently in the Astrophysical Journal alongside another study led by astronomer Yinuo Han from the California Institute of Technology.
“Observing the new Webb data felt like stepping into a dark room and flipping on a light switch. Everything became visible,” Dr. Han remarked.
“Dust is abundant throughout the Webb image, and telescope observations indicate that much of it is fragmenting into repeating and predictable structures.”
Webb’s observations yielded unprecedented images. It produced a clear mid-infrared image revealing a system of four swirling spirals of dust, each expanding in a consistent pattern. Ground-based telescopes had only identified one shell prior to Webb’s discoveries.
By merging Webb imagery with several years of VLT data, they refined the orbital frequency of the star pairs to every 190 years.
Within this remarkably lengthy orbit, the star approaches closely for 25 years, enabling dust formation.
Additionally, Webb’s observations confirmed the existence of three stars that are gravitationally bound to each other in this system.
The dust expelled by the two Wolf-Rayet stars is being cleaved by a third star, a massive supergiant, which creates holes in the dust cloud emanating from its expansive orbit.
“Dr. Webb has provided us with the ‘smoking gun’ evidence to confirm that a third star is gravitationally linked to this system,” Dr. Han noted.
Researchers were aware of this third star since VLT observed its brightest inner shell in 2018, but Webb’s findings helped refine the geometric model and reinforced the connection.
“We unraveled several mysteries with Webb,” Dr. Han added.
“The lingering mystery remains the precise distance from Earth to the star, which will necessitate further observations.”
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Ryan MT White et al. 2025. Snake eating its own tail: Dust destruction of the Apep impact wind nebula. APJ 994, 121; doi: 10.3847/1538-4357/adfbe1
Han Yinuo et al. 2025. JWST reveals the formation and evolution of dust in APEP, a binary star with colliding winds. APJ 994, 122; doi: 10.3847/1538-4357/ae12e5
Source: www.sci.news
