In a groundbreaking collaboration utilizing data from the James Webb Space Telescope (NASA/ESA/CSA) and the European Southern Observatory’s Very Large Telescope (VLT), two distinct scientific collectives have obtained a mid-infrared visualization of a quadruple array of sinuous dust spirals. These structures encircle a binary system comprising two evolved Wolf-Rayet stars, collectively designated as Apep (2XMM J160050.7-514245).
Webb’s mid-infrared image depicts four concentric shells of cosmic dust enveloping a binary pair of Wolf-Rayet stars identified as Apep. The imagery is attributed to NASA, ESA, CSA, STScI, Yinuo Han (Caltech), Ryan White (Macquarie University), and Alyssa Pagan (STScI).
Wolf-Rayet stars represent an infrequent category of substantial binary celestial bodies, serving as the genesis for the universe’s initial carbon isotopes.
It is estimated that only approximately one thousand such stars exist within our Milky Way galaxy, a galaxy that harbors hundreds of billions of stars in its entirety.
Among the several hundred observed Wolf-Rayet binaries to date, the Apep system stands as the solitary instance in our Milky Way Galaxy that contains two Wolf-Rayet stars of this particular nature.
In their recent investigation, astronomer Ryan White from Macquarie University, along with his associates, endeavored to achieve a more precise determination of the orbital paths of the Wolf-Rayet stars within the Apep system.
Their methodology involved integrating refined positional measurements of the dusty rings derived from the Webb imagery with the velocity of the expanding shells, data meticulously collected by the VLT over an eight-year span.
“This celestial configuration is unique, characterized by an extraordinarily prolonged orbital period,” stated White.
“The subsequent longest orbital duration observed in a dusty Wolf-Rayet binary spans approximately 30 years. The majority of such systems exhibit orbital periods ranging from two to ten years.”
The scientific findings of the team were concurrently disseminated in the Astrophysical Journal, accompanied by a complementary publication, spearheaded by Yinuo Han, a researcher at Caltech.
“Contemplating the novel Webb observations felt akin to entering a darkened chamber and illuminating it – every detail became discernible,” remarked Dr. Han.
“The Webb imagery reveals ubiquitous dust, and the telescope has demonstrated that the vast majority of this material was expelled in recurring, predictable patterns.”
The Webb telescope’s observations yielded an unprecedented view: a sharp mid-infrared depiction of a system featuring four interconnected dusty spirals, each unfurling beyond the preceding one in an identical fashion. Prior to Webb’s intervention, ground-based observatories had only identified a single dust shell.
When combined, the Webb imagery and several years of accumulated data from the VLT have served to significantly refine the frequency of the stellar pair’s close encounters, establishing it at once every 190 years.
During each of these exceptionally lengthy orbital cycles, the stars engage in close proximity for a period of 25 years, during which dust is generated.
Furthermore, the Webb observations have corroborated the presence of three celestial bodies gravitationally tethered within this system.
The particulate matter expelled by the two Wolf-Rayet stars is subsequently intersected by a third star, identified as a colossal supergiant. This third star, from its more distant orbital path, sculpts a void within each progressively expanding cloud of ejected dust.
“Webb provided us with the definitive evidence, the ‘smoking gun,’ to confirm that the third star is indeed gravitationally bound to this system,” Dr. Han elucidated.
Astronomers had been aware of the third star’s existence since the VLT captured observations of the most luminous inner shell and the stars in 2018. However, the latest Webb data has facilitated the development of an updated geometric model, thereby solidifying the established connection.
“Several perplexing enigmas have been resolved thanks to Webb,” stated Dr. Han.
“The sole remaining unresolved question pertains to the exact distance separating these stars from Earth, a determination that will necessitate investigations conducted with future observational instruments.”
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Ryan M.T. White et al. 2025. The Serpent Eating Its Own Tail: Dust Destruction in the Apep Colliding Wind Nebula. ApJ 994, 121; doi: 10.3847/1538-4357/adfbe1
Yinuo Han et al. 2025. The Formation and Evolution of Dust in the Colliding-wind Binary Apep Revealed by JWST. ApJ 994, 122; doi: 10.3847/1538-4357/ae12e5
