Stunning New Footage Shows ‘Hard To See Starlight’ In Action

The authors say they “were puzzled at first” until they finally realized they were “seeing something new”.

The results are published in the journal Nature and were obtained using infrared photos of the WR140 binary star system acquired over a period of 16 years.

NASA’s James Webb Space Telescope (JWST) was used in a separate survey of WR140, also published in Nature Astronomy, and was able to see considerably deeper, capturing an image of not just an accelerating dust plume, but of almost twenty, nested inside each other like a large set of onion skins.

WR140 is composed of a large Wolf-Rayet star and an even more massive blue supergiant star that are gravitationally trapped in an eight-year orbit.

This binary star in the constellation Cygnus has been studied for two decades using one of the world’s largest optical telescopes at the Keck Observatory in Hawaii.

Stunning New Footage Shows ‘Hard To See Starlight’ In Action

The WR140 blows plumes of dust that cover thousands of times the distance between the Earth and the Sun. Every eight years, these dust plumes appear, giving astronomers a rare chance to study the effects of starlight on matter.

It is understood that light has momentum and exerts a push on matter known as radiation pressure. Astronomers frequently observe the result of this phenomenon in the form of matter rapidly traversing the cosmos, but it has been difficult to capture this phenomenon in action. In a stellar setting like this, the direct recording of acceleration caused by forces other than gravity is extremely unusual.

“It’s hard to see starlight causing acceleration because the force fades with distance and other forces quickly take over,” says first author Yinuo Han. “To witness an acceleration to the level where it becomes measurable, the material must be reasonably close to the star or the source of the radiation pressure must be very strong. WR140 is a binary star whose fierce radiation field amplifies these effects , placing them within reach of our high-precision data.

All stars have stellar winds, but Wolf-Rayet stars can have winds that are more like hurricanes. Elements in the wind, such as carbon, turn into soot, which stays hot enough to glow in the infrared. Similar to smoke in the wind, this provides telescopes with something to observe.

The interferometry served as a zoom for the mirror of the 10-meter Keck telescope, allowing scientists to obtain sufficiently fine images of WR140 for the survey.

Han and his crew discovered that the stardust does not come out of it in a misty ball with the wind. Instead, the dust originates on the surface of a cone-shaped shock front between the two stars, when the winds of the two stars collide.

The shock front spins in sync with the surrounding binary star. Similar to how water droplets spiral in a lawn sprinkler, the soot plume spins around itself.

Researchers have found that the WR140 has additional capabilities. The two stars do not move in a circle, but rather in an elliptical pattern, and as the binary approaches and leaves the closest point of approach, dust production starts and stops. By modeling these impacts in the three-dimensional geometry of the dust plume, astronomers were able to determine the three-dimensional position of the dust elements.

“Like a clock, this star swells sculpted rings of smoke every eight years, with all that wonderful physics written down and then billowing in the wind like a banner to read,” adds co-author Professor Peter Tuthill. “Eight years later, as the binary returns to its orbit, another appears identical to the previous one, flowing through space inside the bubble of the previous one, like a set of giant nested Russian dolls.”

This Wolf-Rayet has provided astronomers with a unique laboratory to study the Acceleration Zone due to the predictability and expansion of the dust it generates.

“In the absence of external forces, each dust spiral should expand at a constant rate,” adds Han, who is also a co-author of the JWST paper. “We were puzzled at first because we couldn’t fit our model to the observations, until we finally realized we were seeing something new. The data didn’t match because the speed of expansion was not not constant, but rather that it was accelerating. We had captured this for the first time on camera.

“In a way, we always knew that had to be the reason for the flow, but I never imagined we would be able to see physics at work like this,” Tuthill adds. “When I look at the data now, I see the plume of the WR140 unfurling such a giant sail made of dust. When it picks up the wind of photons from the star, like a yacht picking up a gust, it leaps forward suddenly.

Now that JWST is operational, scientists have a great opportunity to learn more about WR140 and other related systems.

According to Ryan Lau, who oversaw the JWST survey, “The Webb Telescope offers new extremes of stability and sensitivity.”

“We will now 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.”

Source: 10.1038/s41586-022-05155-5


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