How do you search for invisible hypothetical particles? One way is to see how quickly they could kill white dwarfs \u2014 the dense, leftover cores of dead stars.<\/p>\n
In recent years, astronomers have become increasingly interested in a theoretical particle known as the axion, which was concocted decades ago to solve a challenging problem with the strong nuclear force<\/a>. After initial attempts to find it in particle collider experiments turned up empty, however, the idea sunk into the background.<\/p>\n <\/p>\n But further research revealed that the axion could be a contender to explain the mystery of dark matter<\/a>. Theorists realized that there might be ways for axions to flood the universe but so far evade direct detection.<\/p>\n You may like<\/p>\n Just because this little particle would be largely invisible, it doesn’t mean it would go completely unnoticed in the universe. In a pre-print paper published in November 2025 in the open access server arXiv<\/a>, researchers reported a way to test axion models using old archival data from the Hubble Space Telescope<\/a>. Although they didn’t find any evidence for axions, they beat other attempts and gave us a much clearer picture of what is and isn’t allowed in this universe.<\/p>\n The targets for this study were white dwarfs<\/a> \u2014 the dense, dim cores of dead stars. A single white dwarf can pack the mass of the sun<\/a> into an object smaller than Earth<\/a>, making white dwarfs among the most exotic objects in the universe. Crucially, white dwarfs support themselves against collapse through something called electron degeneracy pressure, in which a huge sea of free-floating electrons<\/a> resists collapse because, according to quantum mechanics, electrons can never share the same state.<\/p>\n Some models of how axions might behave say these particles could be created by electrons: If an electron were moving quickly enough, it would trigger the formation of an axion. And because the electrons deep inside a white dwarf are moving very, very quickly \u2014 at nearly the speed of light<\/a> \u2014 as they buzz around in their tight confines, they could produce a lot of axions.<\/p>\n The axions would then go speeding off, leaving the white dwarf altogether. This production of escaping axions would rob the white dwarf of energy. And because white dwarfs don’t produce energy on their own, this would cause them to cool off faster than they would otherwise.<\/p>\n The researchers fed this model of axion cooling into a sophisticated software suite that can simulate the evolution of stars<\/a> and how their temperature and brightness change as their interiors evolve.<\/p>\n