Scientists have found why some white dwarf stars stop cooling, challenging previous understandings and impacting how astronomers identify the age of stars. This finding, coming from the behavior of solid crystals within the stars, triggers a reevaluation of excellent age evaluation and galaxy formation theories. Credit: SciTechDaily.comNew research exposes that white dwarf stars stop cooling due to drifting crystals in their interior, offering insights into outstanding aging processes.In a paper published on March 6 in Nature, scholars from the Institute for Advanced Study; the University of Victoria, Canada; and the University of Warwick, U.K., have proposed a new theory that explains why a puzzling population of white dwarf stars stopped cooling for ten billion years.Open any astronomy textbook to the section on white dwarf stars and youll likely learn that they are “dead stars” that continually cool down with time. The cooling takes place since the white overshadows have actually diminished their nuclear heat source. In the traditional picture, this causes the thick plasma in a white dwarfs interior to freeze, leading the star to solidify from the within out.Rethinking White Dwarf Star PhysicsHowever, an analysis of data from the European Space Agencys Gaia satellite, published in 2019 by Sihao Cheng, Martin A. and Helen Chooljian Member in the Institutes School of Natural Sciences, contradicted this basic image. It showed that some white overshadows in truth stay hot for lots of billions of years (a large portion of the age of the Universe). This finding had confused theorists, but todays new paper may supply a compelling explanation.”In order for these white overshadows to stop cooling down, they need to somehow produce extra energy,” states Cheng, who also added to the Nature paper. “Although we were initially uncertain about what this procedure might be, we now have a clearer understanding of how it occurs.”This understanding was developed through a partnership between Cheng, Antoine Bédard of the University of Warwick, and Simon Blouin of the University of Victoria.Representation of white dwarf star V391 Peg. Credit: Chris Laurel, CelestiaThey propose that in some white overshadows, the dense plasma in the interior does not simply freeze from the inside out. Instead, the strong crystals that are formed upon freezing are less thick than the liquid, and therefore start to float towards the surface area. As the crystals drift upwards, they displace the heavier liquid downward. The transport of denser product towards the center of the star launches gravitational energy, and this energy suffices to disrupt the stars cooling process for billions of years.”One interesting element of this discovery is that the physics involved is similar to something we observe in every day life: the frozen crystals within the white dwarf star float instead of sink. We might compare their habits to ice cubes drifting in water,” states Cheng.Why this takes place in some white overshadows and not others is uncertain, but the authors believe it is likely due to the composition of the star.”Some white dwarf stars are formed by the merger of 2 various stars. When these stars clash to form the white dwarf, it alters the composition of the star in such a way that can enable the formation of floating crystals,” states Blouin.Implications of the DiscoveryWhite dwarfs are regularly utilized as age indicators: the cooler a white dwarf is, the older it is assumed to be. However, due to the additional delay in cooling discovered in some white dwarfs, some stars of a provided temperature may be billions of years older than previously thought. Much better understanding the ages and other aspects of white dwarf stars will assist scientists rebuild the formation of our galaxy.”Our work will demand updates to astronomy books,” adds Cheng. “We hope that it will also trigger astronomers to reassess the approaches utilized to calculate the age of excellent populations.”Reference: “Buoyant crystals stop the cooling of white dwarf stars” by Antoine Bédard, Simon Blouin and Sihao Cheng, 6 March 2024, Nature.DOI: 10.1038/ s41586-024-07102-yThe research study is supported by the National Sciences and Engineering Research Council of Canada (NSERC), the Banting Postdoctoral Fellowship program, the European Research Council, the Canadian Institute for Theoretical Astrophysics (CITA), and the Institute for Advanced Studys Fund for Natural Sciences.
Scientists have found why some white dwarf stars stop cooling, affecting and challenging previous understandings how astronomers figure out the age of stars. Credit: SciTechDaily.comNew research study exposes that white dwarf stars stop cooling due to floating crystals in their interior, using insights into stellar aging processes.In a paper released on March 6 in Nature, scholars from the Institute for Advanced Study; the University of Victoria, Canada; and the University of Warwick, U.K., have proposed a brand-new theory that explains why a confusing population of white dwarf stars stopped cooling for 10 billion years.Open any astronomy book to the section on white dwarf stars and youll likely discover that they are “dead stars” that continually cool down over time. In the traditional image, this triggers the dense plasma in a white dwarfs interior to freeze, leading the star to strengthen from the within out.Rethinking White Dwarf Star PhysicsHowever, an analysis of data from the European Space Agencys Gaia satellite, released in 2019 by Sihao Cheng, Martin A. and Helen Chooljian Member in the Institutes School of Natural Sciences, contradicted this standard image. When these stars clash to form the white dwarf, it alters the structure of the star in a method that can enable the formation of drifting crystals,” states Blouin.Implications of the DiscoveryWhite dwarfs are routinely utilized as age indications: the cooler a white dwarf is, the older it is assumed to be.