There could be 14 antimatter objects hidden out there in the Milky Way
On a gamma sky map – the highest energy electromagnetic radiation that passes through our Universe – 14 objects may be hiding a big secret.
In a new analysis of the properties of this radiation, a team of astrophysicists has determined that this is what we would expect from stars made of antimatter – hypothetical objects called antistars.
It would be absolutely huge if this were true – it could help solve one of the Universe’s greatest mysteries, that of all the missing antimatter. But there are still a few other things these 14 items could be.
Every particle of matter that makes up what we see around us – like electrons and quarks – has a counterpart with identical characteristics, except for one thing: an opposite charge. It is believed that particles and antiparticles were produced in equal amounts at the beginning of the Universe.
When a particle and its antiparticle collide, they annihilate each other in an explosion of gamma radiation, suggesting that they should still exist in equal amounts (or nothing exists at all, a happy thought), but for one some reason, only traces of antimatter was detected.
We’ve kind of got used to the idea that hardly any “original” antimatter remains in the Universe. Physicists have developed models and explanations based on this assumption, this is a very big thing.
Then came the experiment with the alpha magnetic spectrometer (AMS-02) aboard the International Space Station. A few years ago he did provisional anthelium detections – a discovery which, if validated, means that enough fundamental antiparticles could have remained in place to agglutinate into whole atoms of antimatter.
But where? According to a team of astronomers led by Simon Dupourqué at the Institute for Research in Astrophysics and Planetology in France, perhaps it is hiding in the form of antistars in the Milky Way.
Because antistars would behave roughly like normal stars, they would be quite difficult to detect – unless normal matter, such as interstellar dust, grew on the star’s surface, where it would be annihilated. by the star’s antimatter.
In turn, this would produce an excess of gamma rays at specific energies that, theoretically, we could detect.
We did not detect the signature annihilation gamma ray bump in the microwave cosmic background (this is the radiation left behind by the Big Bang), nor the Milky Way gamma ray investigations. For their study, Dupourqué and his team focused on 10 years of data from the Fermi Gamma-ray Space Telescope, closely examining the 5,787 gamma-ray sources there for signs of what could be annihilation. matter-antimatter.
They specifically looked for gamma ray signatures compatible with proton-antiproton annihilation, as well as point geometry in the source itself – that is, it looks like a star. Of the 5,787 sources, only 14 could be considered antistar candidates.
It is unlikely that these 14 objects are antistars; they could easily turn out to be emitters of known gamma rays such as pulsars or black holes. But they give us a starting point to estimate how many antistars might be lurking in the Milky Way.
By simulating the processes of antistar accretion and assuming that antistars have properties similar to normal stars, the team derived an upper limit for this number. In the Milky Way’s disk, only 2.5 stars in a million could be antistars.
Outside of the Milky Way disk, in the galactic halo, it could be a very different story. The space above and below the disc is much more free of gas and dust, which means there is less material to accumulate on potential antistars.
Without the accretion of normal matter, these antistars would not give off excess gamma rays and would more easily escape detection in gamma ray investigations; in fact, they could have been hiding from the beginning of the Universe.
According to the team’s calculations, it is unlikely that there are any antistars in the immediate vicinity of the solar system. This means that the source of the anti-helium would more likely be a population of these halo antistars.
You might also have noticed that 2.5 out of 1 million stars are not even close to the equal proportions of antimatter and matter – so finding antimatter stars would not solve the problem of missing antimatter.
In fact, it would likely raise the not insignificant question of how clusters of antimatter managed to survive when surrounded by material that would erase them in a flash of light.
The team’s work aims to provide new, more stringent constraints on the number of antistars that might be available, so that future work has a better working basis to try to understand where and how antiparticles might be found in the field. Milky Way galaxy.
And continuing to monitor these 14 candidates will help determine if they are antistars or something more mundane, like a pulsar or a black hole.
Which is perhaps one of the only times the word “mundane” could apply to these weird, weird objects.
The research was published in Physical examination D.