Beijing time on February 26, according tomedia reports, gamma rays are the brightest and most energetic light in the universe, but the human eye can not see them. Supernova eruptions, neutron star collisions, and hungry black holes all burst into very high-energy gamma-ray radiation in an instant.
The universe is full of explosive, invisible gamma rays (represented in red and yellow). Dark matter may also produce gamma rays, according to a new study.
The gamma rays captured by astronomers with gamma-ray telescopes are all from the most “flammable and explosive” objects in the universe. But a team of international researchers hopes the powerful rays could also point to a more exotic and mysterious substance, the so-called “dark matter.”
In a new study published in the journal Physical Review Letters, researchers looked at the so-called “unidentified gamma ray background”, the remaining faint, mysterious gamma-ray signals in the universe, in addition to gamma rays from known sources such as black holes and supernovae. When the team compared the distribution of unidentified gamma rays with the density maps of the same region sage in the universe, they found that the rays corresponded exactly to the large mass regions of the universe, where dark matter, according to scientists’ predictions, was hidden.
As can be seen from the graph, the two maps are highly coincident, and the density distribution of dark matter (red) is surprisingly consistent with the gamma rays (yellow).
Daniel Gruen, an astrophysicist at the U.S. Department of Energy’s National Accelerator Laboratory at Stanford University, who co-authored the study, said the association suggests that dark matter may be associated with a weak gamma-ray background in the universe. If so, it would provide astronomers with some key clues about the mysterious properties of dark matter.
“Dark matter can decay like a radioactive nucleus and produce gamma rays in the process. “It could be that several dark matter particles collide with each other and produce gamma rays in the process of interaction, ” says Gruen. “
The ripples in the dark
Scientists believe dark matter accounts for 85 percent of the mass of the universe, but researchers still don’t know what they are or where they are. Modern scientific instruments, like blind people in the presence of dark matter, have never been successfully detected.
“However, we already know some of the properties of dark matter. “We know that they are very common in the universe, and that they have masses that can interact with other matter by gravity. “
In other words, although dark matter is not visible, it can have a visible effect on the universe through its own strong gravity. One of these effects, called gravitational lensing, simply means that light emitted by distant galaxies is distorted by the strong gravitational pull of large objects along the way as they make their way to Earth.
In the new study, researchers analyzed a map of gravitational lensing in a particular region of the universe. This map was compiled by the Dark Matter Survey (DES) project. The project’s dedicated camera, mounted on a giant telescope in Chile, took a year to take high-resolution pictures of hundreds of millions of galaxies, focusing on where the light emitted by distant galaxies is most distorted by gravity. In the final compilation of the map, some large mass regions can correspond to known galaxies, but some areas are implicitly showing the effects of dark matter in the dark.
To further understand these effects, the researchers compared this mass map with the gamma-ray distributiondetecti detected in the same area by NASA’s Fermi gamma-ray telescope over the past nine years. The team used mathematical models to remove all of the gamma-ray radiation from “ordinary” sources such as black holes and supernovae, leaving only the mysterious source of “unidentified” gamma rays. After comparing the two maps again, they found that areas with large amounts of gamma-ray radiation significantly coincided with areas with dense mass.
“For the first time in this study, we have confirmed that there is also a large amount of dark matter in the universe where a large amount of gamma rays are distributed. “Gruen suffered.
If dark matter does release gamma rays, it can greatly reduce the difficulty of detecting dark matter and figuring out the composition of dark matter. But Gruen points out that the faint gamma-ray background on the distribution map drawn by the Fermi telescope may also have nothing to do with dark matter, a possibility that cannot be ruled out. The mathematical models they used to cull ordinary gamma rays in the graph are based on assumptions about the nature of celestial bodies such as black holes. But these assumptions may also be false, with distant black holes releasing more gamma rays than researchers have estimated.
“The model may not be perfect enough, and the galaxies in which these black holes are located may be larger than we thought. Gruen pointed out.
The team also needs more data on gamma rays and gravitational lenses to further modify the model and better interpret the cosmic map. Since the study, the Dark Matter Survey has gathered more information about mass distribution in the universe, and the Fermi telescope has been closely tracking gamma-ray bursts along with many other telescopes. Mr Gruen said follow-up studies should be conducted in the coming years, when clearer results will be available.