Deep in the searing core of the colossal star Betelgeuse, a hypothetical kind of dark matter dubbed axions might be brewing and spewing out into the universe — offering scientists the potential for a breakthrough discovery in the ongoing search for evidence of dark matter, according to recent findings presented on April 20 at the American Physical Society's April conference.
A recent analysis seeking signs of the tricky axions turned up empty, but has enabled physicists to place more precise limits on the hypothetical axions' properties.
X-rays emitting from Betelgeuse might point to dark matter
Betelgeuse is a popular star that anyone can see as a bright red dot in the sky within the constellation Orion. It's also close — at 520 light-years from Earth, the giant star made headlines in 2020 when its strange dimming behavior led scientists to suspect it might explode in an unimaginably violent supernova.
While Betelgeuse is hot and large, it could also serve as a perfect candidate for scientists to observe axions — particles of physical conjecture that physicists expect to be a millionth or a billionth the mass of an electron — and might comprise the mysterious dark matter, which vastly outweighs the ordinary matter in our universe — despite having an almost wholly-unknown nature.
Axions shouldn't interact often with luminous — or ordinary — matter. But some theories think photons (light particles) might convert back and forth into axions inside a strong magnetic field, according to Physicist Mengjiao Xiao of the Massachusetts Institute of Technology (MIT) in Cambridge, in a Live Science report. Stars have a thermonuclear core — which makes them a great place to find extremely high numbers and levels of photons and magnetism. Betelgeuse is 20 times our sun's mass, which might make it "what we call an axion factory," added Xiao.
If Betelgeuse's core produces axions, they should be capable of escaping the star's gravity, and stream in our direction en masse. And, interacting with the Milky Way galaxy's magnetic field, the axions might then convert back into photons in the X-ray field of the spectrum of electromagnetic radiation, said Xiao to Live Science. Betelgeuse is no spring chicken. It is known. But the bright side of the star's age is that it shouldn't emit a lot of X-ray light — which means any X-ray light coming from the aging star might indicate the presence of dark matter — in the form of axions.
Detecting dark matter axions might tell us when Betelgeuse will go supernova
NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) in space enabled Xiao and his colleagues to seek out signs of X-rays hailing from Betelgeuse, but sadly they saw nothing besides typical astrophysical processes like the tiny amount of X-rays still credibly produced by the colossal star. But the new findings presented on April 20 hint that axions and photons are at least three times less likely to interact in the predicted ways than scientists thought.
If researchers spot the hoped-for X-rays emitting from a star, it wouldn't necessarily mean axions are real. Scientists would still have to show that these rays aren't coming from non-dark-matter sources before conventional physics is exhausted, leaving dark matter as the only remaining explanation, said Joshua Foster, an MIT physicist, to Live Science.
Regardless, scientists may still find dark matter axions. If or when they do, astronomers would greatly advance our understanding of Betelgeuse, said Xiao. Additionally, if we can identify dark matter axions coming from Betelgeuse, we might finally be able to calculate when the colossal and aging star will go supernova. And when it comes to explosions of this cosmic scale, you don't have to be interested in the mysteries of the universe to enjoy the show.