There are things that our detectors cannot see, like dark matter. This is why you have to look to different ways to try and find certain particles. In this case, scientists are hunting for the elusive axion, and to do this, they used data taken by NASA’s NuSTAR telescope of one of our favorite stars, Betelgeuse.

NuStar is capable of focusing high-energy X-rays, and the team collected 50 kiloseconds of data from Betelgeuse. The reason they chose this star is that, as we all learned last year, Betelgeuse is on the verge of going supernova, astronomically speaking. And we hypothesized that axions will be produced by stars in this condition, and those axions will interact with magnetic fields and briefly couple to photons in the X-ray band, giving us a chance to “see” them. Since axions are a theoretical superlight particle that makes up dark matter, we cannot expect to see them otherwise.

This new paper was published in Physical Review Letters, and coauthor Kerstin Perez explains further: Betelgeuse is at a temperature and lifestage where you don’t expect to see X-rays coming out of it, through standard stellar astrophysics. But if axions do exist, and are coming out, we might see an X-ray signature. So that’s why this star is a nice object: If you see X-rays, it’s a smoking gun signal that it’s got to be axions.

Unfortunately, the team came up empty-handed, but a null data set is still a data set, and these results put new constraints on just where and how we can find axions. Perez sums up the lack of discovery: What our results say is, if you want to look for these really light particles, which we looked for, they’re not going to talk very much to photons. We’re basically making everyone’s lives harder because we’re saying, ‘you’re going to have to think of something else that would give you an axion signal.’

Now scientists will have to use other, less detectable energy bands to try and find these axion signals. If only Beteguese would actually go supernova, then we could see if the explosion pushes the axions to couple with gamma rays. Meanwhile, the search for axions continues.

More Information

MIT press release

“Constraints on Axionlike Particles from a Hard X-Ray Observation of Betelgeuse,” Mengjiao Xiao et al., 2021 January 21, Physical Review Letters