JWST reveals Apep: four serpentine dust shells around a rare Wolf‑Rayet system

NASA’s James Webb Space Telescope has captured a striking mid‑infrared view of the Apep system — a rare multi‑star system about 8,000 light‑years away that shows four serpentine shells of dense carbon dust. Previous observations suggested a single shell, but Webb’s sensitivity reveals multiple layers and dramatic structure shaped by stellar winds.

The shells were produced by two Wolf‑Rayet stars — massive, evolved stars losing mass via powerful winds — over roughly the last 700 years. New analyses combining Webb data with years of observations from the European Southern Observatory’s Very Large Telescope (VLT) indicate the two Wolf‑Rayets orbit one another every ~190 years and pass closely for about 25 years, a configuration that drives intense wind collisions and dust production.

Key findings

• Four dust shells: Webb’s mid‑IR image shows concentric, serpentine carbon‑rich shells; the outermost shell reaches the edges of the image.
• Binary dynamics: The Wolf‑Rayet pair completes a long, eccentric orbit (~190‑year period) and creates dust during close passages lasting ~25 years.
• Third star discovered: Webb confirmed a massive supergiant (40–50× the Sun) gravitationally bound to the pair; it carves a funnel‑like cavity in the shells.
• Stellar evolution: The Wolf‑Rayet stars have shed much of their initial mass and currently weigh about 10–20 solar masses; they are expected to explode as supernovae in the future and may leave behind black holes.

Why Apep is important

Apep offers a rare laboratory for studying how massive stars lose mass, form dust, and interact dynamically in multi‑star systems. Wolf‑Rayet stars are uncommon — only about a thousand are known in our galaxy — and systems like Apep help astronomers test models of wind collisions, dust formation, and the conditions that precede supernova explosions.

How researchers studied it

Researchers combined Webb’s mid‑infrared imaging with archival and new observations from the VLT to trace the system’s geometry and dynamics. The high angular resolution and sensitivity of Webb in the mid‑IR were crucial to resolving the faint, extended shells and the cavity carved by the supergiant companion.

What’s next

• Follow‑up spectroscopy and time‑series imaging to refine masses, wind properties and dust composition.
• Monitoring the system for changes as the binary moves through its eccentric orbit and potentially enters another dust‑forming phase.
• Theoretical modeling to link observed shell morphology to wind speeds, orbital parameters and dust production mechanisms.

For more from JWST and the observatories involved, see NASA’s Webb site and the European Southern Observatory (links open in a new tab): NASA Webb • ESO.

Discussion: Which aspect of Apep fascinates you most — the layered dust shells, the rare Wolf‑Rayet stars, or the system’s future as potential supernovae/black holes? What would you like telescopes to observe next?