\n
![\"EarthSnap\"\/](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2025\/12\/earthsnap-banner-news.webp.webp\")
\n<\/a><\/p>\n
Few stars at this stage of life are close enough to be examined carefully, which is why researchers focused on this one. R. Doradus is located 180 light-years \u2013 or about 1.1 quadrillion miles \u2013 away.<\/p>\n
The work was led by Theo Khouri, an astronomer at Chalmers University of Technology (Chalmers<\/a>) in Gothenburg.<\/p>\n His research follows how old stars shed gas \u2013 material that later becomes the raw feedstock for new planets.<\/p>\n Why stellar winds matter<\/p>\n Giant stars lose mass in stellar wind<\/a>, a steady flow of gas leaving a star, long before they fade away.<\/p>\n That outflow<\/a> carries carbon, oxygen, and nitrogen outward, and later stars and planets can reuse those atoms.<\/p>\n If astronomers misread what launches the wind, they also misread how fast galaxies get chemically enriched.<\/p>\n For decades, many models assumed radiation pressure<\/a>, force from light pushing on matter, could shove newborn dust outward.<\/p>\n As grains accelerate, they collide with nearby gas and drag it along, which builds a wider wind.<\/p>\n That picture works well for some carbon-rich stars, but oxygen-rich giants like R Doradus<\/a> have been harder to explain.\u00a0<\/p>\n Observing stardust in color<\/p>\n The team used polarized light<\/a>, light waves lined up in one direction, to isolate faint dust close to the star.<\/p>\n In November of 2017, the experts observed the dust in visible colors with the SPHERE instrument on the Very Large Telescope at Paranal, Chile.\u00a0<\/p>\n The years that followed were spent carefully analyzing the data and testing whether it truly supported long-standing theories.<\/p>\n Because the technique separates scattered starlight from glare, researchers can measure dust where the wind starts accelerating.<\/p>\n Color patterns and grain sizes<\/p>\n Subtle changes across wavelengths revealed how dust reflected light, and the color pattern pointed to grain sizes.<\/p>\n The scattered signal matched mostly silicates, minerals built from silicon and oxygen, and also alumina dust near the star.<\/p>\n Those compositions fit what oxygen-rich giants can condense, but composition alone cannot reveal whether the grains can escape.<\/p>\n Testing stardust with simulations<\/p>\n The team used radiative transfer models \u2013 mathematical simulations of how light moves through dust and gas \u2013 to link the telescope images to the underlying physics.<\/p>\n The experts tracked photon scattering and absorption around the star, and then predicted polarization patterns for different grain sizes.<\/p>\n Matching those patterns to the telescope data provided a strict limit on how much push starlight can deliver.<\/p>\n Small grains can\u2019t drive stellar wind<\/p>\n Dust grains smaller than the star\u2019s light wavelength don\u2019t catch enough light to push gas outward. <\/p>\n When the team calculated the forces, they found gravity still held the gas in place \u2013 meaning these tiny grains can\u2019t drive the stellar wind.<\/p>\n \u201cWe thought we had a good idea of how the process worked. It turns out we were wrong. For us as scientists, that\u2019s the most exciting result,\u201d said Khouri.<\/p>\n The team compared dust demands to a gas-to-dust ratio in the envelope, meaning how much gas exists for each dust mass.<\/p>\n Even if every available silicon or aluminum atom locked into solids, the models still fell short of driving the wind.<\/p>\n When iron-rich dust heats<\/p>\n Iron-rich grains absorb more starlight, which raises the force, but absorption also raises their temperature.<\/p>\n At high temperatures, sublimation<\/a> \u2013 solid material turning directly into gas \u2013 removes those grains before they can accelerate gas.<\/p>\n That tradeoff leaves iron-bearing dust as a poor driver near R Doradus, even if it could help farther out.<\/p>\n Bubbles and pulses push gas<\/p>\n Churning convection<\/a>, hot material rising and cooler material sinking, can lift gas into cooler layers above the star\u2019s surface.<\/p>\n Rhythmic swelling of the star can also send shocks outward, and shock-compressed gas can start flowing away.<\/p>\n Those processes may hand dust an easier job by lifting gas where new grains can form and catch light.<\/p>\n Stars with repeated cycles<\/p>\n R Doradus brightens and dims on repeating cycles, so the wind launch zone may look different month to month.<\/p>\n The star pulsates \u2013 regularly swelling and shrinking \u2013 with cycles of roughly 175 and 332 days.<\/p>\n If dust formation spikes during certain phases, a snapshot from one observing season may miss short-lived bursts.<\/p>\n Stardust still plays a role<\/p>\n Dust does not need to drive the whole wind to matter, because grains can cool gas and block heat.<\/p>\n In condensation, gas molecules sticking together into solids, alumina can seed silicates that grow as they drift outward.<\/p>\n If another mechanism first lifts gas, even modest dust pressure could help set the final mass-loss rate.<\/p>\n Turning starlight into wind<\/p>\n Stars like the Sun eventually shed outer layers and leave a white dwarf<\/a>, the dense core left after a star sheds layers.<\/p>\n Before that quiet end, many such stars pass through the asymptotic giant branch phase and lose huge amounts of gas.<\/p>\n That uncertainty forces models to treat the Sun\u2019s distant future cautiously, because its own wind will shape the final planetary system.<\/p>\n Taken together, the observations and models show that tiny dust around R Doradus cannot turn starlight into a strong wind.<\/p>\n Future campaigns across many pulsation phases should test when other forces dominate, and whether dust helps more in faster-losing giants.<\/p>\n The study is published in the journal Astronomy & Astrophysics<\/a>.<\/p>\n Image Credit: ESO\/T. Schirmer\/T. Khouri; ALMA (ESO\/NAOJ\/NRAO)<\/p>\n \u2014\u2013<\/p>\n Like what you read? Subscribe to our newsletter<\/a> for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"For decades, scientists thought dust helped aging stars push gas into space \u2013 but a nearby star shows…\n","protected":false},"author":2,"featured_media":375107,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[49],"tags":[199,79],"class_list":{"0":"post-375106","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-physics","9":"tag-science"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/375106","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/comments?post=375106"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/375106\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media\/375107"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media?parent=375106"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/categories?post=375106"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/tags?post=375106"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}