Search for axions from nearby star Betelgeuse comes up empty

Results significantly narrow the range of possible places to find the hypothetical dark matter particles.

Jennifer Chu | MIT News Office
January 21, 2021

The elusive axion particle is many times lighter than an electron, with properties that barely make an impression on ordinary matter. As such, the ghost-like particle is a leading contender as a component of dark matter — a hypothetical, invisible type of matter that is thought to make up 85 percent of the mass in the universe.

Axions have so far evaded detection. Physicists predict that if they do exist, they must be produced within extreme environments, such as the cores of stars at the precipice of a supernova. When these stars spew axions out into the universe, the particles, on encountering any surrounding magnetic fields, should briefly morph into photons and potentially reveal themselves.

Now, MIT physicists have searched for axions in Betelgeuse, a nearby star that is expected to burn out as a supernova soon, at least on astrophysical timescales. Given its imminent demise, Betelgeuse should be a natural factory of axions, constantly churning out the particles as the star burns away.

However, when the team looked for expected signatures of axions, in the form of photons in the X-ray band, their search came up empty. Their results rule out the existence of ultralight axions that can interact with photons over a wide range of energies. The findings set new constraints on the particle’s properties that are three times stronger than any previous laboratory-based axion-detecting experiments.

“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,” says Kerstin Perez, assistant professor of physics at MIT. “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.’”

Perez and her colleagues have published their results today in Physical Review Letters. Her MIT co-authors include lead author Mengjiao Xiao, Brandon Roach, and Melaina Nynka, along with Maurizio Giannotti of Barry University, Oscar Straniero of the Abruzzo Astronomical Observatory, Alessandro Mirizzi of the National Institute for Nuclear Physics in Italy, and Brian Grefenstette of Caltech.