Astronomers have discovered an unexpected and unexplained feature outside our Milky Way galaxy that emits high-energy light called gamma rays.
The team behind the discovery, including NASA and University of Maryland cosmologist Alexander Kashlinsky, discovered the gamma-ray signal while searching 13 years of data from NASA’s Fermi telescope.
“This is a completely serendipitous discovery,” Kasilinski said. stated in a statement. “We found a much stronger signal in another part of the sky than what we were looking for.”
What makes this gamma-ray signal even more bizarre is that it points towards another unexplained feature of the universe, the source of some of the most energetic cosmic particles ever detected. It’s a fact.
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The research team believes the newly discovered signal is related to these high-energy particles, which are primarily composed of protons, neutrons, and atomic nuclei, or cosmic rays.
These ultra-high-energy cosmic rays (UHECRs) carry more than a billion times more energy than gamma rays, and their origin remains one of the greatest mysteries in astrophysics, and the discovery of this gamma-ray source deepens the mystery.
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This new mysterious gamma-ray signature may be similar to the unique properties of the cosmic microwave background (CMB).
The CMB represents the oldest light in the universe and is a cosmic fossil left over from an event that occurred approximately 380,000 years after the Big Bang. Before this, the universe was a hot, thick soup of free electrons and protons through which light could not pass.
But around this time, the universe cooled enough for electrons and protons to combine to form primordial atoms. The sudden lack of free electrons meant that photons, particles of light, could no longer be scattered endlessly by these negatively charged particles.
The universe virtually instantaneously went from opaque to transparent, allowing the first light to travel. The CMB consists of these first free-moving photons.
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As the universe expanded over the next 13.8 billion years or so, these photons lost energy and now have a uniform temperature of -454 degrees Fahrenheit (-270 degrees Celsius).
CMB was first discovered in May 1964 by American radio astronomers Robert Wilson and Arno Penzias as microwave radiation in all directions above the Earth’s sky. However, in the 1990s, this apparent uniformity was called into question when NASA’s Cosmic Background Explorer (COBE) discovered small fluctuations in his CMB temperature.
According to COBE, the CMB was found to be 0.12% hotter and more microwave-rich than average in the direction of the constellation Leo, and 0.12% cooler and less microwave-rich than average in the opposite direction.
This pattern, or “dipole,” in the CMB is thought to result from the solar system’s 230 miles per second motion relative to the fossil radiation field. But if this is the case, similar dipoles caused by the solar system’s motion should occur in any light from astrophysical sources far beyond the solar system, which has not been observed to date. .
Astronomers are looking for this effect in other types of light so they can confirm that the CMB dipole is a result of our motion.
“Such measurements are important because the discrepancy in the size and orientation of the CMB dipole allows us to explore physics that could date back to the very beginning of the universe, when it was less than a trillionth of a second old. “It gives us a glimpse into the process,” said team member Fernando Atrio Barrandera, a professor of theoretical physics at the University of Salamanca in Spain.
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The research team focused on Fermi and its Large Area Telescope (LAT). The telescope will scan the entire sky above Earth several times a day, collecting and collating data over many years. The researchers expected to find a radiation pattern of dipoles detectable with gamma rays embedded within the LAT data.
Due to the influence of special relativity and the high-energy nature of gamma rays, such dipoles should be five times more pronounced in this data than in the CMB’s lower-energy microwave light. The team found something similar to this pattern, but not what they expected.
“We have discovered a gamma-ray dipole, but its peak is far away from the CMB in the southern sky.” [peak], and its size is 10 times larger than what we would expect from its motion,” said team member Chris Schroeder, an astrophysicist at the Catholic University of America. Similar features have been reported for the highest energy cosmic rays. ”
The shower of high-energy charged particles that make up UHECR reach Earth has a corresponding dipole, which was first discovered in 2017 by Argentina’s Pierre Auger Observatory.
These charged particles are deflected by the Milky Way’s magnetic field and other magnetic fields as they move toward Earth, and the strength of this deflection depends on the particle’s energy and its charge, but the UHECR dipole still remains where it is. It will peak at It is similar to the location where Kasilinski and his colleagues discovered the gamma ray source.
The researchers theorize that this correlation in location means that the mysterious gamma rays and UHECR are likely related, especially considering that unidentified sources are causing both phenomena.
Astronomers are now investigating the location of these emissions to determine the source of this ultra-high-energy light and these ultra-high-energy particles, and to determine if they are actually related and how they resolve. We want to see if it represents one of the mysteries of the universe. two.
The team’s findings were presented by Kashlinski at the 243rd meeting of the American Astronomical Society in New Orleans, Louisiana, and discussed in a paper. paper Published Wednesday (January 10) in The Astrophysical Journal Letters.