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Inside dying red giants, large aging stars that have expanded after exhausting core hydrogen, vibrations revealed magnetic fields buried far below the surface.<\/p>\n
By linking those signals to later observations, Lukas Einramhof, Ph.D. student in astrophysics at the Institute of Science and Technology Austria, (ISTA<\/a>), showed that the same fields can reemerge on white dwarf surfaces.<\/p>\n Those results hold only when magnetism extends across a broad interior region rather than remaining confined to a small central zone.<\/p>\n That constraint narrows the possible origins of stellar magnetism and sets up the deeper explanation that follows.<\/p>\n Starquakes and magnetism<\/p>\n Astronomers read those hidden layers through asteroseismology<\/a>, the use of starquakes to probe a star\u2019s interior, in red giants.<\/p>\n Those vibrations change when magnetism blocks some internal waves, letting researchers infer fields far below the visible surface.<\/p>\n Hundreds of low-luminosity red giants in a 2024 survey showed signs of buried core magnetism, giving the new model a firmer starting point.<\/p>\n \u201cBecause a white dwarf is the exposed core of a red giant that has shed its outer layers, these different observations essentially examine the same region of a star\u2019s interior at different evolutionary stages,\u201d said Einramhof.<\/p>\n A broader core<\/p>\n Field<\/a> strength alone did not solve the puzzle, because the model needed magnetism to occupy more of the star.<\/p>\n In the red giants anchoring the calculations, inferred fields matched magnetic signals already seen in starquakes, natural oscillations in a star that reveal its internal structure.<\/p>\n That broader radiative zone, a stable layer where energy moves mostly as light, let weaker ancient fields remain relevant.<\/p>\n \u201cHowever, this doesn\u2019t mean the stars are more strongly magnetized, only that the magnetic fields must already reach a larger portion of their core,\u201d Einramhof said.<\/p>\n Shells not centers<\/p>\n As the star<\/a> swelled and reworked its inside, the magnetic field no longer stayed strongest at the center.<\/p>\n The simulations showed a shell-like layout, with the field compressed into a hollow layer near a zone of active fusion.<\/p>\n By the time white dwarf cooling began, that layer sat about 35 percent of the way out from the core.<\/p>\n That geometry matters because it can reach the surface after millions of years, instead of staying buried too long.<\/p>\n Old remnants answer<\/p>\n Old white dwarfs had posed the mystery for years, because magnetism appeared more often as these stellar remnants aged.<\/p>\n Nearby surveys showed white dwarfs<\/a> rarely showed magnetism early, then increasingly did so after one to three billion years.<\/p>\n That delay fit a fossil field, a magnetic field preserved from youth, better than a signal created only at the end.<\/p>\n The model does not erase other ideas, but it gives ancient magnetism a stronger claim on the evidence.<\/p>\n Ruling out shortcuts<\/p>\n One popular route now looks too narrow, because fields born only in a young star\u2019s churning core stayed buried.<\/p>\n By the red giant phase, those fields sat below the layer that starquakes can sense most clearly.<\/p>\n Those results ruled out a simple core<\/a> dynamo, a field generator driven by moving charged gas, as the full answer.<\/p>\n It also failed to explain two very young magnetic white dwarfs, reminding astronomers that more than one route may exist.<\/p>\n Rewriting stellar aging<\/p>\n A durable inner field could do more than survive, because magnetism can redirect motion, heat, and matter inside stars.<\/p>\n When magnetic forces stir material across layers, fresh hydrogen can move inward and keep nuclear burning going longer.<\/p>\n For our own Sun<\/a>, a 4.6-billion-year-old star, that possibility matters, because it will also pass through red giant and white dwarf stages.<\/p>\n Any forecast of stellar lifetimes, rotation, or internal mixing stays incomplete until astronomers know how common these hidden fields really are.<\/p>\n The Sun\u2019s core<\/p>\n The Sun sits at the heart of that uncertainty, because nobody has yet measured whether its deep core is magnetic.<\/p>\n \u201cWe still don\u2019t know whether the sun\u2019s core is magnetic,\u201d Einramhof said, framing the biggest unknown behind these stellar forecasts.<\/p>\n If strong fields pull hydrogen inward, the Sun could burn that fuel longer than standard models now assume.<\/p>\n A magnetic core could also alter rotation and internal mixing, so even a familiar star keeps one major secret.<\/p>\n What remains hidden<\/p>\n The model still leaves important loose ends, because nobody yet knows whether the shell-like field stays stable for billions of years.<\/p>\n It also left out some later episodes, including a short-lived churning core that forms during helium fusion.<\/p>\n Answering both problems will require 3D simulations, full computer models that track structure, and more magnetic measurements in young white dwarfs.<\/p>\n Those tests could show whether fossil fields are common, rare, or just one piece of a messier magnetic history.<\/p>\n Star magnetism across ages<\/p>\n From subtle vibrations inside aging stars to magnetism on their compact remnants, the evidence now points to a single long-lived internal process.<\/p>\n Future observations will decide how often stars keep that inheritance and when it breaks, reshaping forecasts for stars, remnants, and the Sun.<\/p>\n The study is published in Astronomy & Astrophysics<\/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":"Researchers have found that magnetic fields buried deep inside stars can survive their entire lifetimes and later reappear…\n","protected":false},"author":2,"featured_media":384868,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[111,139,69,147],"class_list":{"0":"post-384867","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-new-zealand","9":"tag-newzealand","10":"tag-nz","11":"tag-science"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/384867","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=384867"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/384867\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/384868"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=384867"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=384867"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=384867"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}