Astrophysicists using NASAs Chandra X-ray Observatory have looked for signs of an as-yet undetected particle predicted by string theory, a set of models intended to tie together all known forces, particles, and interactions.<\/p>\n
Reynolds et al used Chandra to look for extraordinarily low-mass axion-like particles in the Perseus galaxy cluster, a group of galaxies located 240 million light-years away from Earth. The observation lasting over five days showed no evidence for certain axion-like particles, which some theorists think can explain dark matter. The lack of detection in these Chandra observations helps rule out some versions of string theory, a set of models intended to tie together all known forces, interactions, and particles. Image credit: NASA \/ CXC \/ University of Cambridge \/ Reynolds et al.<\/p>\n
Until recently I had no idea just how much X-ray astronomers bring to the table when it comes to string theory, but we could play a major role. If these particles are eventually detected it would change physics forever, said studys lead author Dr. Christopher Reynolds, a researcher at the University of Cambridge.<\/p>\n
The particle that Dr. Reynolds and colleagues were searching for is called an axion.<\/p>\n
This as-yet-undetected particle should have extraordinarily low mass. Theoretical physicists do not know the precise mass range, but many theories feature axion masses ranging from about a millionth of the mass of an electron down to zero mass.<\/p>\n
Some scientists think that axions could explain the mystery of dark matter, which accounts for the vast majority of matter in the universe.<\/p>\n
One unusual property of this ultra-low-mass particle would be that it might sometimes convert into photons (that is, packets of light) as they pass through magnetic fields. The opposite may also hold true: photons may also be converted into axions under certain conditions.<\/p>\n
How often this switch occurs depends on how easily they make this conversion, in other words on their convertibility.<\/p>\n
Some scientists have proposed the existence of a broader class of ultra-low-mass particles with similar properties to axions.<\/p>\n
Axions would have a single convertibility value at each mass, but axion-like particles would have a range of convertibility at the same mass.<\/p>\n
While it may sound like a long shot to look for tiny particles like axions in gigantic structures like galaxy clusters, they are actually great places to look, said studys co-author Dr. David Marsh, a researcher at Stockholm University.<\/p>\n
Galaxy clusters contain magnetic fields over giant distances, and they also often contain bright X-ray sources. Together these properties enhance the chances that conversion of axion-like particles would be detectable.<\/p>\n
To look for signs of conversion by axion-like particles, the astrophysicists examined over five days of Chandra observations of X-rays from material falling towards the supermassive black hole in the center of NGC 1275, the central galaxy of the Perseus galaxy cluster.<\/p>\n
They studied the Chandra spectrum, or the amount of X-ray emission observed at different energies, of this source.<\/p>\n
The long observation and the bright X-ray source gave a spectrum with enough sensitivity to have shown distortions that scientists expected if axion-like particles were present.<\/p>\n
The lack of detection of such distortions allowed the researchers to rule out the presence of most types of axion-like particles in the mass range their observations were sensitive to, below about a millionth of a billionth of an electrons mass.<\/p>\n
Our research doesnt rule out the existence of these particles, but it definitely doesnt help their case, said studys co-author Dr. Helen Russell, a researcher at the University of Nottingham.<\/p>\n
These constraints dig into the range of properties suggested by string theory, and may help string theorists weed their theories.<\/p>\n
The results appear in the Astrophysical Journal.<\/p>\n
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Christopher S. Reynolds et al. 2020. Astrophysical Limits on Very Light Axion-like Particles from Chandra Grating Spectroscopy of NGC 1275. ApJ 890, 59; doi: 10.3847\/1538-4357\/ab6a0c<\/p>\n
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Astrophysicists Perform Test of String Theory | Astronomy - Sci-News.com<\/a><\/p>\n","protected":false},"excerpt":{"rendered":" Astrophysicists using NASAs Chandra X-ray Observatory have looked for signs of an as-yet undetected particle predicted by string theory, a set of models intended to tie together all known forces, particles, and interactions. Reynolds et al used Chandra to look for extraordinarily low-mass axion-like particles in the Perseus galaxy cluster, a group of galaxies located 240 million light-years away from Earth. The observation lasting over five days showed no evidence for certain axion-like particles, which some theorists think can explain dark matter Continue reading