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In the new study, the crucial evidence came from an oxygen-burning shell, a layer where oxygen fuel releases heat.<\/p>\n
By tracking that layer at Kyoto University<\/a>, astronomer Ryota Shimada showed magnetic fields could reverse spin flow.<\/p>\n Before the reversal, magnetism carried spin outward. After it, the same forces moved spin inward and the shell sped up.<\/p>\n The result does not prove every massive star behaves this way, but it exposes a missing rule in many stellar life-cycle models.<\/p>\n Layers can lose or gain spin<\/p>\n Stars do not carry spin evenly. Angular momentum<\/a>, the stored spin an object carries, can move between layers.<\/p>\n Inside a convection zone \u2013 a churning layer of hot and cooler gas \u2013 flowing material carries heat and drags magnetic fields.<\/p>\n Those tugs act through Maxwell stress, magnetic tension that transfers spin, so fields can brake one layer while feeding another.<\/p>\n Because the same layer can lose or gain spin, magnetism cannot be treated only as a spin-down force.<\/p>\n A clear pattern emerged<\/p>\n A key control point was the Rossby number<\/a>, a measure comparing a layer\u2019s rotation with its churning motion.<\/p>\n When that number stayed above one, magnetic stress pulled spin outward and helped the shell slow down.<\/p>\n After the number dropped below one, the magnetic pattern flipped and sent spin inward instead through the shell.<\/p>\n Earlier dynamo theory, which explains magnetic fields born from moving gas, made that reversal plausible beyond this single model.<\/p>\n Confirming the spin pattern <\/p>\n To make the discovery useful, Shimada\u2019s team turned the three-dimensional behavior into a one-dimensional model<\/a>, a simplified radial star calculation.<\/p>\n That model used rotation, density, and nuclear heat release to estimate where magnetic stress would send spin inside the shell.<\/p>\n The model predicted the inward turn around 340 seconds, close to the simulation\u2019s 350-second reversal.<\/p>\n Matching both direction and strength matters because stellar-evolution codes<\/a>, programs that follow stars through time, cannot run full three-dimensional interiors.<\/p>\n Why spin matters<\/p>\n Spin can influence what kind of remnant a massive star leaves when its central core finally collapses.<\/p>\n Fast rotation can help power unusually strong explosions, while slower cores better fit neutron stars, dense collapsed remnants.<\/p>\n Magnetic prescriptions used in earlier core-spin models<\/a>, calculations of stellar core rotation, mostly treated magnetism as an outward spin drain.<\/p>\n A field that sometimes feeds spin back inward makes the final core rate harder to predict.<\/p>\n Lessons from the Sun<\/p>\n The Sun has long tied magnetism to the slow loss of stellar spin because it is close enough to measure.<\/p>\n Magnetized stellar winds<\/a>, charged outflows from stars, carry material away and drain surface spin over time.<\/p>\n By reading stellar vibrations, asteroseismology<\/a> later showed many stars lose interior spin faster than simple models expected.<\/p>\n \u201cWe suspected that the flow inside the massive star\u2019s convective zone may evolve analogously with the solar convective zone,\u201d said Shimada.<\/p>\n What earlier simulations showed<\/p>\n Earlier computer simulations<\/a> from 2023 already showed magnetic fields could grow fast inside late-stage massive stars before their collapse.<\/p>\n In one run, oxygen-shell fields reached about 100 billion gauss \u2013 a magnetic-strength unit \u2013 within 180 seconds. Neon-shell fields reached half that.<\/p>\n Those fields suppressed mixing, reduced nuclear fuel<\/a> at the shell base, and quickly pushed the layers toward rigid rotation.<\/p>\n The new research adds the missing inward case, so earlier outward-only rules now look incomplete for some massive stars.<\/p>\n Limitations of the study <\/p>\n One simulation cannot map every star, especially because real stars differ in mass, fuel layering, and rotation.<\/p>\n The calculation covered a short late-life window, not the full birth-to-death history of a star. Neon and carbon shells in the run had not settled enough to test the same rule cleanly.<\/p>\n \u201cSlow rotation might even be forbidden in some classes of massive stars,\u201d said Lucy McNeill, a co-author of the study at Kyoto University.<\/p>\n Future research directions <\/p>\n Future tests must place the new rule inside full stellar-life calculations that follow many masses, stages, and starting spin rates.<\/p>\n Such calculations would show whether inward magnetic transport survives beyond one oxygen-shell episode in different massive stars.<\/p>\n They also need better treatment of chemical mixing<\/a>, the way burning products and fresh fuel blend.<\/p>\n Without that piece, modelers may predict a spin rate while missing the fuel changes that set the stress.<\/p>\n Dying stars now look less predictable because magnetism can move spin inward or outward inside layered, burning interiors before collapse.<\/p>\n Better models could improve supernova forecasts, but only if future simulations test the rule across more stars.<\/p>\n The study is published in The Astrophysical Journal<\/a>.<\/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":"A dying massive star can regain spin deep inside itself instead of simply slowing down, according to new…\n","protected":false},"author":2,"featured_media":617500,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[49],"tags":[199,79],"class_list":["post-617499","post","type-post","status-publish","format-standard","has-post-thumbnail","category-physics","tag-physics","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/617499","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=617499"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/617499\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media\/617500"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media?parent=617499"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/categories?post=617499"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/tags?post=617499"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}