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Stars made with antimatter could lurk in the Milky Way

A new study suggests that fourteen punctures of light on a gamma-ray sky map could fit into the bill of anti-stars, stars made with antimatter.

These anti-star candidates appear to be detached from the type of gamma rays that occur when antimatter — the opposite charged charge of matter — encounters normal, annihilating matter. This could occur on the surfaces of anti-stars as their gravity attracts the normal matter of interstellar space, researchers reported online on April 20 in Physical Review D.

"If, by chance, the existence of anti-stars can be proved … that would be a great blow to the standard cosmological model," says Pierre Salati, a theoretical astrophysicist at the Annecy-le-Vieux Theoretical Physics Laboratory in France and not involved. at work. "It would really imply a significant change in our understanding of what happened in the primitive universe."

It is generally thought that although the universe was born with equal amounts of matter and antimatter, the modern universe contains almost no antimatter (SN: 24/03/20). Physicists typically think that as the universe evolved, some process led to matter particles greatly exceeding their antimatter alter egos (SN: 11/25/19). But an International Space Station instrument recently questioned this assumption by detecting evidence of some anti-helium nuclei. If such observations are confirmed, such lost antimatter could be spilled by anti-stars.

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Intrigued by the possibility that some antimatter in the universe survived in the form of stars, a team of researchers examined 10 years of observations from the Fermi gamma-ray space telescope. Among the catalog's nearly 5,800 gamma-ray sources, 14 points of light emitted gamma rays with expected matter-antimatter annihilation energies, but they did not look like any other type of gamma-ray source, such as a pulsar or black hole.

Based on the number of candidates observed and the sensitivity of the Fermi telescope, the team calculated how many anti-stars could exist in the solar district. If there were anti-stars inside the plane of the Milky Way, where they could accumulate a lot of gas and dust made of ordinary matter, they could emit a lot of gamma rays and be easy to detect. As a result, the handful of detected candidates would imply that there is only one anti-star for every 400,000 normal stars.

If, on the other hand, anti-stars tended to exist outside the plane of the galaxy, they would have much less chance of accumulating normal matter and would be much harder to find. In that scenario, there could even be an anti-star lurking among every 10 normal stars.

But proving that any celestial object is an anti-star would be extremely difficult, because in addition to the gamma rays that could arise from matter-antimatter annihilation, the light emitted by anti-stars is expected to resemble the light of normal stars. “It would be virtually impossible to say that (the candidates) are really anti-stars,” says Simon Dupourqué, co-author of the study, an astrophysicist at the Research Institute of Astrophysics and Planetology in Toulouse, France. "It would be much easier to deny."

Astronomers could see how the candidates ’gamma rays or radio signals change over time to verify that these objects are not actually pulsars. Researchers could also look for optical or infrared signals that could indicate that the candidates are actually black holes.

“Obviously, this is still preliminary … but it’s interesting,” says Julian Heeck, a physicist at the University of Virginia in Charlottesville who doesn’t participate in the work.

The existence of anti-stars would imply that substantial amounts of antimatter somehow managed to survive in isolated space bags. But Heeck doubts that, if they existed, anti-stars would be abundant enough to account for all the antimatter missing in the universe. "I would still need an explanation of why matter dominates over antimatter in general."

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