The seek for a hypothetical subatomic particle that might sign new physics simply narrowed a bit — due to the sunshine swirling round a gargantuan black gap in one other galaxy.
The light-weight particle — dubbed the axion — has been proposed as an answer to the thriller of why the universe has so little antimatter and as a candidate for the elusive darkish matter that fills the cosmos (SN: 3/24/20; SN: 3/6/20). The twisting and chaotic environs of galaxy M87’s central black gap, the primary black gap to have its image taken, are thought to encode details about such particles.
Now, the particulars of how gentle round M87’s black gap is oriented may rule out the probability of axion particles in a selected mass vary, researchers report March 17 in Nature Astronomy. This examine additionally reveals that scientists may use an identical technique in upcoming astrophysical observations to seek for these particles in an assortment of plenty.
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“It’s a very exciting idea,” says physicist Benjamin Safdi of the University of California, Berkeley, who was not concerned with this examine. “They’ve come up with a new method, and they’ve shown that this method could in principle work.”
First proposed within the late Seventies, axions have but to be present in experiments. Theoretical work since that preliminary proposal has proven an prolonged household of axions may exist, every selection having a unique mass however all interacting weakly with odd matter. In 2020, physicist Yifan Chen of the Chinese Academy of Sciences in Beijing and colleagues described a solution to search for axions utilizing observations of the sunshine surrounding black holes.
According to idea, a quickly spinning black gap can construct up a dense clumping of axion particles within the quick surrounding space. Precisely which kinds of axions get constructed up depends upon the width of the black gap. And the supermassive black gap in M87 has the fitting dimension for brewing a stew of ultralightweight axionlike particles. If this black gap certainly kicked up such a cloud, that may change the orientation, or polarization, of the sunshine coming from that area. In explicit, the polarization would wobble over time.
Unfortunately, nobody had any pictures of polarized gentle from a black gap to look at — till final 12 months. That’s when the Event Horizon Telescope, or EHT, an Earth-spanning community of radio telescopes, revealed its picture of the polarized gentle across the supermassive black gap on the middle of M87 (SN: 3/24/21).
This “is precisely the information that we need in order to carry out this theoretical proposal,” says particle physicist Yue Zhao of the University of Utah in Salt Lake City. “We have a very extreme condition that can produce a huge amount of axions, and we have the right tool to study the signature of the axion.”
So Zhao, Chen and colleagues examined the EHT information for a time-varying change within the polarization’s path. While a cloud of axions would alter the path, so too will the energetic and turbulent area across the black gap. This is a “kind of unavoidable background that we have to deal with,” Zhao says. Once they eliminated that from the overall sign, they discovered that there’s not sufficient of a further wobble to say any sign may have come from the axion cloud. They dominated out the existence of ultralightweight axions with a mass of about 10 billionths of a billionth of a billionth of an electron’s mass.
But the identical approach could possibly be used to hunt for different axionlike particles. “The larger black hole you have, the lighter is your mass,” Zhao says. The physicists hope to make use of the EHT’s future observations of different black holes to search for axions of various plenty. One black gap on EHT’s radar is the behemoth on the middle of our personal galaxy, Zhao notes, which is about one-thousandth the mass of M87’s (SN: 6/5/19). If our galaxy’s monster black gap has a cloud of axions, these can be heavier particles.
“This idea of looking for these axionlike particles, is, in my opinion, the most exciting thing happening in particle physics at the moment,” says Safdi.
