Space Dust Pushed By Starlight Observed For The First Time
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A star pair in our galaxy shows how ambient light matters.Everyone can see firsthand how light pressure from a star changes the cosmic dust flow. This is the first time I’ve
This radiation pressure affects how dust is expelled from regions near young stars, directing the formation of gas clouds around dying stars (SN: 09/22/20) . The dust patterns surrounding a star pair 5,600 light-years away in Cygnus provide a rare laboratory to see the effect in action. Astronomers have long known that the dust emitted by the star WR 140 and its companion arises from the collision and condensation of gas from these two stars into soot. But this pair of images, taken over a period of 16 years, shows that the dust is accelerating as it moves away from the star.
Researchers report that dust initially leaves the star at about 4 million miles per hour, accelerating to about 6 million miles per hour over the course of a year. At that speed, dust can travel from the Sun to Earth in just 15 hours.
The revelation came from comparing the positions of concentric dust shells from year to year and deriving the velocities. The researchers’ calculations show that the force accelerating the dust is the pressure exerted by the light emitted by the star, said Han of the University of Cambridge. “Radiation pressure becomes visible only when you put all the images side by side.”
These dust layers not only feel the pressure of light, but also extend far beyond what any telescope can see – until this year. Images from the James Webb Space Telescope (JWST) show more dusty layers around WR 140 and its allies than ever before, Han and another team said in his October 12 Nature Reported in Astronomy.
At first glance, the intricate patterns surrounding the stars look like giant spider webs. But researchers’ analysis shows they’re actually giant, expanding, cone-shaped dust shells. They are nested within each other, forming a new one every eight years as the star completes another orbital journey. In the new image, the shell is viewed from the side, making it look like it’s part of a ring, says Han.
The pattern does not completely surround the star because the distance between stars changes as they orbit each other. When stars are far away, the colliding gas is too dense to condense into dust. This is the effect the researchers expected.
To their surprise, the gas didn’t condense well when the star was at its closest. This suggests that there is a ‘Goldilocks zone’ in the dust formation. Dust only forms when the stars are spaced just right, creating a series of concentric dust shells that recede from the duo.
“Your Goldilocks zone is a new idea,” says astrophysicist Andy Pollock of the University of Sheffield, UK. “The same thing happens with my X-ray field.”
In his study, Pollock observed that his WR 140 and its partners emit more of his X-rays as the stars get closer to each other, but less when they get very close. good. “It will be interesting to see if there is a connection between the two Goldilocks zones,” he says. “It all has to fit somehow.”