(ORDO NEWS) — When the New Horizons probe reached the outer darkness of the solar system, beyond Pluto, its instruments picked up something strange.
The very, very faint space between the stars glowed with optical light. . This in itself was not unexpected; this light is called the cosmic optical background, the faint glow of all light sources in the universe outside our galaxy.
The odd part was the amount of light. There were significantly more of them than scientists thought – in fact, twice as many.
Now, in a new paper, scientists lay out a possible explanation for the excess of optical light: a by-product of dark matter interactions that are otherwise undetectable.
“The results of this work,” writes a team of researchers led by astrophysicist José Luis Bernal of Johns Hopkins University, “provide a potential explanation for the excess cosmic optical background that is allowed by independent observational constraints, and it could answer one of the oldest unknowns in cosmology: nature dark matter.”
We have a lot of questions about the universe, but dark matter is one of the most annoying. This is the name we give to the mysterious mass in the universe responsible for providing much more gravity at concentrated points than it should be.
Galaxies, for example, rotate faster than they should be under the influence of gravity created by the mass of visible matter.
The curvature of space-time around massive objects is greater than it should be if we calculated the curvature of space based only on the amount of luminous material.
But whatever creates this effect, we can’t detect it directly. The only way to know that it exists is that we simply cannot explain this extra gravity.
And there’s a lot of her. Approximately 80 percent of the matter in the universe is dark matter.
There are several hypotheses about what it might be. One candidate is the axion, which belongs to a hypothetical class of particles first conceptualized in the 1970s to address the question of why strong atomic interactions follow so-called charge-parity symmetry, although most models say this is not necessary.
As it turns out, axions in a certain mass range should also behave exactly the way we expect dark matter to behave. And there may be a way to detect them, because theoretically, axions are expected to decay into pairs of photons in the presence of a strong magnetic field.
Several experiments are looking for sources of these photons, but they must also flow through space in excess.
The difficulty is to separate them from all other light sources in the universe, and this is where the cosmic optical background comes in.
The background itself is very difficult to detect as it is very dim. The Long Range Reconnaissance Camera (LORRI) aboard New Horizons is arguably the best tool for this job.
It’s far from Earth and the Sun, and LORRI is far more sensitive than the instruments attached to the more distant Voyager probes launched 40 years ago.
The scientists speculated that the excess found by New Horizons was due to the product. to stars and galaxies that we cannot see. And this option is still very relevant. The work of Bernal and his team was to evaluate whether axion-like dark matter could be the cause of the extra light.
They performed mathematical modeling and determined that axions with masses between 8 and 20 electron volts could produce extra light. observable signal under certain conditions.
This is incredibly small for a particle that is usually measured in mega-electronvolts. But with recent estimates estimating the hypothetical fraction of matter in fractions of one electron volt, these numbers would require axions to be relatively powerful.
It is impossible to tell which explanation is correct based on current data alone. However, by narrowing down the axion masses that may be responsible for the excess, the researchers have laid the foundation for future searches for these enigmatic particles.
“If the excess results from the decay of dark matter at the photon line, there will be a significant signal in upcoming mapping measurements of the line intensity,” the researchers wrote.
“In addition, the ultraviolet instrument aboard New Horizons (which will have better sensitivity and explore a different range of the spectrum) and future studies of very high energy gamma ray attenuation will also test this hypothesis and extend the search for dark matter to a wider frequency range.”
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