James Webb Telescope detects a star shedding its carbon envelope

The James Webb Space Telescope has studied the amazing Wolf-Rayet 140 system, which consists of two massive and hot stars. Scientists have learned that powerful dust shells form here and contain large amounts of carbon.

Carbon shells. Source: phys.org

Dust shells of stars

Astronomers have long been trying to track how elements such as carbon, essential for life, become widespread in the Universe. Now NASA’s James Webb Space Telescope has taken a closer look at one of the current sources of carbon-rich dust in our Milky Way galaxy: Wolf-Rayet 140, a system of two massive stars that move in a tight, elongated orbit.

As they fly one past the other (within the center white dot in telescope images), stellar winds from each star compress, material is compressed, and carbon-rich dust is formed. Recent observations by James Webb show 17 dust shells glowing in mid-infrared light that regularly expand into the surrounding space.

“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, lead author of a new paper on the subject and a doctoral student at the University of Denver in Colorado.

Cyclic mechanism

Each shell rushes away from the stars at more than 1,600 miles per second (2,600 kilometers per second), nearly 1% faster than 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 of the study and 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.”

Like clockwork, stellar winds generate dust for a few months every eight years when the pair makes its closest approach during a wide, elongated orbit. James Webb also shows how dust formation is changing, note the darker area at the top left in both images.

Images of shells

Mid-infrared telescope images have revealed shells that have been around for more than 130 years. (Older shells have dissipated so much that they are now too faint to detect.) The researchers hypothesize that the stars will eventually generate tens of thousands of dust shells over hundreds of thousands of years.

The distribution of dust is not uniform. Although not obvious at first glance, when we zoom in on the shells in James Webb’s images, we can see that a portion of the dust has “accumulated” to form amorphous, fragile clouds that are the size of our entire solar system. 

Many other individual dust particles float freely. Each speck of dust is one hundredth the width of a human hair. Whether condensed or not, all dust travels at the same speed and is rich in carbon.

Future of this system

What happens to these stars millions or billions of years from now, after they have finished “sawing” their surroundings with dust? The Wolf-Rayeе star in this system is 10 times more massive than the Sun and is nearing the end of its life. In its final “act,” this star will either explode as a supernova – possibly lifting some or all of the dust envelope – or collapse into a black hole that will leave the dust envelope intact.

While no one can predict with certainty what will happen, researchers are rooting for a black hole scenario.

“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.”

According to phys.org

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