Using the James Webb Space Telescope, astronomers have captured the dynamic process of carbon-rich dust formation around Wolf-Rayet 140, a binary star system in our galaxy.
How is carbon, a key building block of life, produced and distributed across space? Using the James Webb Space Telescope, astronomers have identified a stellar duo just 5,000 light-years away in the Milky Way responsible for creating carbon-rich dust. In the Wolf-Rayet 140 system, two massive stars orbiting in an elongated path collide their stellar winds during close passes, generating carbon-rich dust. Every eight years, this process forms a new shell of dust that expands outward and could eventually contribute to the creation of new stars elsewhere in the galaxy.
Webb’s mid-infrared imaging has captured 17 distinct dust shells around the stars, though many older shells may have dissipated over time, and thousands more are expected to form in the future. These discoveries provide critical insights into carbon’s origins and how such elements contribute to the formation of new stars and planets.
Compare the two mid-infrared images taken by the James Webb Space Telescope of Wolf-Rayet 140, a system of dust shells ejected by two massive stars that are in an elongated orbit.
Look to the top right of the first two images. Two triangles are matched up to show how much difference 14 months makes: The dust is racing away from the central stars at almost 1% the speed of light and no longer lines up in the third image.
When the winds of the massive stars, which are buried within the white central region in the first and second images, collide and that material compresses, it forms carbon-rich dust that moves away from the stars. This occurs for a few months during each eight-year orbit, which is one reason why the dust isn’t “sprayed” equally around the stars to form complete shells.
Credit: NASA, ESA, CSA, STScI, Emma Lieb (University of Denver), Ryan Lau (NSF’s NOIRLab), Jennifer Hoffman (University of Denver)
Webb Space Telescope Watches Carbon-Rich Dust Shells Form, Expand in Star System
For years, astronomers have sought to understand how life-essential elements like carbon spread across the universe. NASA’s James Webb Space Telescope has now provided a closer look at an active source of carbon-rich dust within our Milky Way: Wolf-Rayet 140, a binary system of two massive stars locked in a tight, elongated orbit.
As these stars approach one another, their powerful stellar winds collide, compressing material and triggering the formation of carbon-rich dust. Webb’s detailed observations reveal 17 distinct dust shells, glowing in mid-infrared light, expanding outward in regular, rhythmic intervals into space.
This video alternates between two James Webb Space Telescope observations of Wolf-Rayet 140, a two-star system that has sent out more than 17 shells of dust over 130 years. Mid-infrared light observations highlight them with excellent clarity. By comparing this pair of observations, taken only 14 months apart, researchers showed the dust in the system has expanded. All the dust in every shell is moving at almost 1% of the speed of light. The stars are very bright, which led to the diffraction spikes in both images. These are artifacts, not meaningful features.
Rapid Expansion of Dust Shells
“The telescope not only confirmed that these dust shells are real, its data also showed that the dust shells are moving outward at consistent velocities, revealing visible changes over incredibly short periods of time,” said Emma Lieb, the lead author of the new paper and a doctoral student at the University of Denver in Colorado.
Every shell is racing away from the stars at more than 1,600 miles per second (2,600 kilometers per second), almost 1% the speed of light. “We are used to thinking about events in space taking place slowly, over millions or billions of years,” added Jennifer Hoffman, a co-author and a professor at the University of Denver. “In this system, the observatory is showing that the dust shells are expanding from one year to the next.”
When the two massive stars in Wolf-Rayet 140 swing past one another, their winds collide, material compresses, and carbon-rich dust forms. The stronger winds of the hotter Wolf-Rayet star blow behind its slightly cooler (but still hot) companion. The stars create dust for several months in every eight-year orbit. Credit: NASA, ESA, CSA, Joseph Olmsted (STScI)
The Clockwork of Dust Formation
Like clockwork, the stars’ winds generate dust for several months every eight years, as the pair make their closest approach during a wide, elongated orbit. Webb also shows how dust formation varies — look for the darker region at top left in both images.
The telescope’s mid-infrared images detected shells that have persisted for more than 130 years. (Older shells have dissipated enough that they are now too dim to detect.) The researchers speculate that the stars will ultimately generate tens of thousands of dust shells over hundreds of thousands of years.
“Mid-infrared observations are absolutely crucial for this analysis, since the dust in this system is fairly cool. Near-infrared and visible light would only show the shells that are closest to the star,” explained Ryan Lau, a co-author and astronomer at NSF NOIRLab in Tuscon, Arizona, who led the initial research about this system. “With these incredible new details, the telescope is also allowing us to study exactly when the stars are forming dust — almost to the day.”
The dust’s distribution isn’t uniform. Though this isn’t obvious at first glance, zooming in on the shells in Webb’s images reveals that some of the dust has “piled up,” forming amorphous, delicate clouds that are as large as our entire solar system. Many other individual dust particles float freely. Every speck is as small as one-hundredth the width of a human hair. Clumpy or not, all of the dust moves at the same speed and is carbon-rich.
Long-Term Fate of the Star System
What will happen to these stars over millions or billions of years, after they are finished “spraying” their surroundings with dust? The Wolf-Rayet star in this system is 10 times more massive than the Sun and nearing the end of its life. In its final “act,” this star will either explode as a supernova — possibly blasting away some or all of the dust shells — or collapse into a black hole, which would leave the dust shells intact.
Though no one can predict with any certainty what will happen, researchers are rooting for the black hole scenario. “A major question in astronomy is, where does all the dust in the universe come from?” Lau said. “If carbon-rich dust like this survives, it could help us begin to answer that question.”
“We know carbon is necessary for the formation of rocky planets and solar systems like ours,” Hoffman added. “It’s exciting to get a glimpse into how binary star systems not only create carbon-rich dust, but also propel it into our galactic neighborhood.”
These results have been published in the Astrophysical Journal Letters and were presented in a press conference at the 245th meeting of the American Astronomical Society in National Harbor, Maryland.
Reference: “Dynamic Imprints of Colliding-wind Dust Formation from WR 140” by Emma P. Lieb, Ryan M. Lau, Jennifer L. Hoffman, Michael F. Corcoran, Macarena Garcia Marin, Theodore R. Gull, Kenji Hamaguchi, Yinuo Han, Matthew J. Hankins, Olivia C. Jones, Thomas I. Madura, Sergey V. Marchenko, Hideo Matsuhara, Florentin Millour, Anthony F. J. Moffat, Mark R. Morris, Patrick W. Morris, Takashi Onaka, Marshall D. Perrin, Armin Rest, Noel Richardson, Christopher M. P. Russell, Joel Sanchez-Bermudez, Anthony Soulain, Peter Tuthill, Gerd Weigelt and Peredur M. Williams, 13 January 2025, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/ad9aa9
The James Webb Space Telescope is humanity’s most advanced space observatory, unlocking the secrets of our solar system, distant worlds, and the origins of the universe. Operated through a partnership between NASA, ESA, and CSA, Webb is helping us understand the cosmos and our place within it like never before.
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