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How do you seek for invisible hypothetical particles? A method is to see how rapidly they may kill white dwarfs — the dense, leftover cores of useless stars.
Lately, astronomers have change into more and more excited about a theoretical particle often known as the axion, which was concocted many years in the past to resolve a difficult drawback with the sturdy nuclear drive. After preliminary makes an attempt to seek out it in particle collider experiments turned up empty, nevertheless, the concept sunk into the background.
Simply because this little particle can be largely invisible, it doesn’t suggest it could go utterly unnoticed within the universe. In a pre-print paper printed in November 2025 within the open entry server arXiv, researchers reported a option to check axion fashions utilizing outdated archival information from the Hubble House Telescope. Though they did not discover any proof for axions, they beat different makes an attempt and gave us a a lot clearer image of what’s and is not allowed on this universe.
The targets for this research had been white dwarfs — the dense, dim cores of useless stars. A single white dwarf can pack the mass of the solar into an object smaller than Earth, making white dwarfs among the many most unique objects within the universe. Crucially, white dwarfs help themselves in opposition to collapse by one thing known as electron degeneracy strain, wherein an enormous sea of free-floating electrons resists collapse as a result of, based on quantum mechanics, electrons can by no means share the identical state.
Some fashions of how axions would possibly behave say these particles might be created by electrons: If an electron had been shifting rapidly sufficient, it could set off the formation of an axion. And since the electrons deep inside a white dwarf are shifting very, in a short time — at practically the pace of sunshine — as they buzz round of their tight confines, they may produce loads of axions.
The axions would then go dashing off, leaving the white dwarf altogether. This manufacturing of escaping axions would rob the white dwarf of power. And since white dwarfs do not produce power on their very own, this might trigger them to chill off sooner than they might in any other case.
The researchers fed this mannequin of axion cooling into a classy software program suite that may simulate the evolution of stars and the way their temperature and brightness change as their interiors evolve.
This mannequin allowed the researchers to foretell the standard temperature of a white dwarf, given its age, each with and with out axion cooling. With the leads to hand, they turned to information of the globular cluster 47 Tucanae collected with Hubble. International clusters are essential as a result of all the white dwarfs in them had been born at roughly the identical time, giving the astronomers a big pattern to check.
Briefly, the researchers discovered no proof for axion cooling within the white dwarf inhabitants. However their outcomes did give brand-new constraints on the power for electrons to supply axions: They can not do it extra effectively than as soon as each trillion possibilities.
This consequence does not rule out axions solely, nevertheless it does say it is unlikely that electrons and axions immediately work together with one another. So, if we’ll hold looking for axions, we’ll have to seek out much more intelligent methods to look.
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