Evidence of a long-sought hypothetical particle could have been hidden from view (X-rays) all this time.
X-ray emissions from a collection of neutron stars known as the Magnificent Seven is so excessive that they could come from the axes, a much-predicted type of particle, forged in the dense nuclei of these dead objects, have shown scientists.
If their findings are confirmed, this discovery could help unravel some of the mysteries of the physical universe – including the nature of the mysterious dark matter that holds them all.
“Finding the axes was one of the major efforts in high-energy particle physics, both in theory and in experiments,” said astronomer Raymond Co of the University of Minnesota.
“We believe that the axioms could exist, but we have not discovered them yet. You can think of actions as ghost particles. They can be anywhere in the Universe, but they don’t interact strongly with us, so we don’t have any observations of them yet. “
Axes are hypothetical particles with ultra-low mass, first theorized in the 1970s to solve why strong atomic forces follow something called charge parity symmetry, when most models say they don’t need it.
Axions are predicted by many models of string theory – a proposed solution to the tension between general relativity and quantum mechanics – and the axes of a specific mass are also a strong candidate for dark matter. So scientists have a number of very good reasons to look for them.
If any, the axioms are expected to be produced inside the stars. These stellar axioms are not the same as dark matter axioms, but their existence would imply the existence of other types of axioms.
One way to look for axes is to look for excess radiation. Axes are expected to decompose into photon pairs in the presence of a magnetic field – so if more electromagnetic radiation is detected than it should be in a region where this decay is expected to occur, this could be evidence of the actions. .
In this case, the excess X-rays is exactly what astronomers discovered when looking at the Magnificent Seven.
These neutron stars – the collapsed nuclei of dead massive stars that have died in a supernova – are not grouped together, but share a number of features in common. All are isolated neutron stars from about the Middle Ages, a few hundred thousand years after stellar death.
They all cool down, emitting low (soft) energy X-rays as they do so. All have strong magnetic fields, billions of times stronger than Earth’s, strong enough to trigger axial decay. And they are all relatively close, less than 1,500 light-years from Earth.
This makes it an excellent laboratory for looking for axes, and when a team of researchers – led by author and senior physicist Benjamin Safdi of Lawrence Berkeley National Laboratory – studied Magnificent Seven with several telescopes, they identified the large X (hard) energy – the emission of rays is not expected for neutron stars of this type.
However, there are many processes in space that can produce radiation, so the team had to carefully examine other potential emission sources. Pulsars, for example, emit harsh X-rays; but other types of pulsed radiation, such as radio waves, are not present in the Magnificent Seven.
Another possibility is that unresolved sources near neutron stars could produce harsh X-ray emissions. But the data sets used by the team from two different space X-ray observatories – XMM-Newton and Chandra – indicated that the emission came from neutron stars. The team found that the signal could not be the result of an accumulation of soft X-ray emissions either.
“We are pretty sure that there is this excess and we are very confident that there is something new among this excess,” Safdi said. “If we were 100% sure that what we see is a new particle, it would be huge. It would be revolutionary in physics.”
This does not mean that the excess is a new particle. It could be a previously unknown astrophysical process. Or it could be something as simple as a telescope artifact or data processing.
“We do not claim to have made the discovery of the axion yet, but we say that the additional X-ray photons can be explained by the axes,” said Co. “It’s an interesting discovery of excess X-ray photons and it’s an interesting possibility, which is already consistent with our interpretation of axes.”
The next step will be to try to verify the finding. If the excess is produced by the axes, then most of the radiation should be emitted at higher energies than XMM-Newton and Chandra are able to detect. The team hopes to use a newer NASA NuSTAR telescope to observe the Magnificent Seven over a wider range of wavelengths.
Magnetized white dwarf stars could be another place to look for axial emissions. Like the Magnificent Seven, these objects have strong magnetic fields and are not expected to produce harsh X-rays.
“This is starting to get pretty convincing that this is something beyond the standard model if we see an excess of X-rays in there as well,” Safdi said.
The research was published in Physical review letters.