The light from stars can push matter. The dust generated by the violent interactions between two stars was tracked by researchers from the universities of Cambridge and Australia.
The results are reported in a journal.
In a study published in Nature Astronomy, NASA's James Webb Space Telescope (JWST) was able to see much deeper and snap an image of almost 20 of them, nested inside each other.
There is a huge Wolf-Rayet star and a blue supergiant star in this picture. One of the world's largest optical telescopes is located in Hawaii and has been used to monitor this star for two decades.
Dust stretches thousands of times the distance from the Earth to the Sun. Astronomers have a chance to observe how starlight affects matter.
Light exerts a push on matter called radiation pressure. It has been difficult to catch on to the phenomenon of matter coasting at high speeds around the universe. In a stellar environment, direct recording of acceleration due to forces other than gravity is extremely rare.
Yinuo Han from Cambridge's Institute of Astronomy is the author of the Nature paper. The material needs to be close to the star or the source of the radiation pressure needs to be stronger. The effects of the radiation field are within reach of our high-precision data.
The stars from Wolf-Rayet can be more like hurricanes. Carbon in the wind becomes soot, which glows bright in the IR. It's like smoke in the wind and telescopes can see it.
The team used a technology called interferometry which was able to act like a zoom lens for the 10-meter Keck telescope mirror, allowing them to recover sufficiently sharp images of the study.
Han and his team found that the dust does not come out of the star with the wind. The wind from the two stars collide on the surface of a cone-shaped shock front.
The shock front rotates because the star is in motion. In the same way that a garden sprinkler creates a spiral, the sooty plume gets wrapped into a spiral.
The researchers found that the company has more tricks up its sleeves. Dust production turns on and off as the two stars near each other and leave the closest approach. The location of dust features in three-dimensional space was measured by modelling these effects into the three-dimensional geometry.
"This star puffs out sculpted smoke rings every eight years, with all this wonderful physics written then inflated in the wind like a banner for us to read," said co-author Professor Peter Tuthill. After eight years, the same thing appears as it did eight years ago, like a set of giant nested Russian dolls.
The dust produced by the Wolf-Rayet is so predictable that it gave the astronomer a unique laboratory to look at the acceleration zone.
In the absence of external forces, each dust spiral should expand at a constant speed. We were puzzled at first because we couldn't fit our model to the observations, until we realized that we were seeing something new. The data didn't fit because the expansion speed wasn't constant but it was speeding up. For the first time, we caught that.
"In one sense, we always knew this must be the reason for the outflow, but I never imagined we'd be able to see the physics at work like this." I see a giant sail made of dust when I look at the data now. It makes a sudden jump forward when it catches the wind from the star.
Researchers can learn a lot more about the systems now that the JWST is up and running. Ryan Lau who led the study said that the telescope offers new extremes of stability and sensitivity. "We'll be able to make observations like this much more easily than from the ground, opening a new window into the world of Wolf- Rayet physics."
More information: Yinuo Han et al, Radiation-driven acceleration in the expanding WR140 dust shell, Nature (2022). DOI: 10.1038/s41586-022-05155-5. www.nature.com/articles/s41586-022-05155-5Nested dust shells were observed around the Wolf–Rayet binaries. The article can be found at www.nature.com.
Journal information: Nature , Nature Astronomy
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