Stunning new James Webb image shows off a unique star system that creates a dust ring every 8 years

"We’re looking at over a century of dust production from this system."
Chris Young
The two stars in Wolf-Rayet 140 and their shells of dust.
The two stars in Wolf-Rayet 140 and their dust rings.

Source: NASA, ESA, CSA, STScI, JPL-Caltech 

A stunning new James Webb image reveals at least 17 dust rings emanating from a rare type of binary star system.

That's not an optical illusion caused by Webb's cameras; the new image captures a duo of stars, known as Wolf-Rayet 140, some 5,000 light-years from Earth, and the ghostly ripple rings created by their interacting solar winds.

A unique feature of this particular star system is that it only creates one dust ring every eight years due to the way the stars orbit each other, NASA explains in a blog post.

Analyzing a new James Webb image

The stars orbit each other once every eight years, and one dust ring is created during each orbit, meaning the dust rings mark the passage of time in a similar fashion to a tree trunk.

"We’re looking at over a century of dust production from this system," explained Ryan Lau, an astronomer at NSF's NOIRLab and lead author of a new study on the phenomenon published in the journal Nature Astronomy. "The image also illustrates just how sensitive this telescope is. Before, we were only able to see two dust rings, using ground-based telescopes. Now we see at least 17 of them."

James Webb's Mid-Infrared Instrument (MIRI) is well suited to studying the dust rings around Wolf-Rayet 140 because it detects the longest infrared wavelengths, meaning it can see cooler objects like the dust rings.

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The Wolf-Rayet 140 system contains a type of star called a Wolf-Rayet star. This is an O-type star, which is born with roughly 25 times more mass than our Sun and is nearing the end of its life. These stars typically form a black hole when they die.

How gas turns into dust in space

In its blog post, NASA explains the process of gas transforming into dust in space, comparing it to turning flour into bread. The process "requires specific conditions and ingredients," NASA explains. "The most common element found in stars, hydrogen, can’t form dust on its own. But because Wolf-Rayet stars shed so much mass, they also eject more complex elements typically found deep in a star’s interior, including carbon. The heavy elements in the wind cool as they travel into space and are then compressed where the winds from both stars meet, like when two hands knead dough."

Though other Wolf-Rayet systems form dust, there is no other documented system that makes rings in the same way as Wolf-Rayet 140. The system creates dust rings periodically — once every eight years — due to the fact that their orbit is elongated and not circular. Once every eight years, the stars come close enough together — roughly the same distance between Earth and the Sun — for their stellar winds to collide, putting the gas under enough pressure to form dust. If its orbit were circular and closer together, it would form dust continuously.

The new study also suggests that Wolf-Rayet stars produce carbon-rich dust molecules, based on data obtained using MIRI's Medium Resolution Spectroscopy mode. The image of Wolf-Rayet 140 isn't the first James Webb image of ghostly ripple rings surrounding a Wolf-Rayet star. Last month, NASA released a similar image of a star called WR140, which is also surrounded by ripples. Astronomers estimate there should be a few thousand Wolf-Rayet stars in our galaxy, meaning James Webb will likely provide more similar images in the not-too-distant future.

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