There may be 14 antimatter objects hiding in the Milky Way. These objects are called anti-stars.

[SergUpstart]

On the map of the gamma-ray sky - the electromagnetic radiation of the highest energy flowing through our universe-14 objects can hide a big secret. In a new analysis of the properties of this radiation, a team of astrophysicists determined that it is consistent with what we expect from stars made of antimatter - hypothetical objects known as anti-stars. If this were true, it would be absolutely incredible - it could help solve one of the biggest mysteries in the universe, namely, all the missing antimatter. But there are a few other things that these 14 objects could be. Every particle of matter that makes up the material we see around us, such as electrons and quarks, has an analog with identical characteristics, except for one thing: the opposite charge. It is believed that particles and antiparticles were produced in equal quantities at the beginning of the universe. When a particle and its antiparticle collide, they annihilate each other in a burst of gamma radiation, which suggests that they should still exist in equal amounts (or it doesn't exist at all), but for some reason only trace amounts of antimatter are not detected. We're kind of used to the idea that virtually none of the "original" antimatter remains in the universe. Physicists have developed models and explanations based on this assumption. This was followed by an experiment with the Alpha Magnetic Spectrometer (AMS-02) on board the International Space Station. A few years ago, a preliminary detection of antihelium was made - a discovery that, if confirmed, means that enough fundamental antiparticles could remain to cluster into whole antimatter atoms. But where? According to a group of astronomers led by Simon Dupurcke from the Institute for Research in Astrophysics and Planetary Science in France, it may be hiding in the form of anti-stars in the Milky Way. Since anti-stars will behave much like normal stars, they will be quite difficult to detect-unless normal matter, such as interstellar dust, accrets on the star's surface, where it will be annihilated by the star's antimatter. In turn, this will lead to an excess of gamma radiation at certain energies that we could theoretically detect. We did not detect the signature of annihilating gamma-ray radiation in the cosmic microwave background (this is the radiation left over from the Big Bang) or the gamma-ray surveys of the Milky Way. For their study, Dupurcke and his team focused on 10 years of data from the Fermi Space Gamma-ray Telescope, closely examining the 5,787 gamma-ray sources in it to find signs of what could be the annihilation of matter and antimatter. They specifically looked for gamma-ray signatures corresponding to the annihilation of the proton and antiproton, as well as the point geometry in the source itself, that is, it looks like a star. Of the 5,787 sources, only 14 can be considered anti-star candidates. It is unlikely that these 14 objects are anti-stars; they could easily be known gamma-ray emitters, such as pulsars or black holes. But they give us a starting point for estimating the number of anti-stars that may be lurking in the Milky Way. By simulating the accretion processes of anti-stars and assuming that they have properties similar to normal stars, the team deduced an upper limit for this number. In the disk of the Milky Way, only 2.5 stars out of a million can be anti-stars. Outside the Milky Way disk, in the galactic halo, things could have been very different. The space above and below the disk is much more empty of gas and dust, which means that any potential anti-stars accumulate less material. Without the accretion of normal matter, these anti-stars would not emit an excess of gamma radiation, and it would be easier for them to evade detection in gamma-ray surveys; in fact, they could have been hiding since the beginning of the universe. According to the team's calculations, it is unlikely that there are any anti-stars in the immediate vicinity of the Solar System. This means that the source of the antihelium is likely to be a population of these halo-anti-stars. You may also have noticed that 2.5 out of 1 million stars are not even equal proportions of antimatter and matter, so discovering stars from antimatter won't solve the problem of missing antimatter. In fact, this is likely to raise the important question of how the antimatter clumps were able to survive being surrounded by material that would destroy them in a flash of light. The team's work aims to set new, tighter limits on the number of anti-stars that can be there, so that future work has a better foundation to work on, trying to understand where and how anti-particles can be found in the Milky Way galaxy. And continuing to observe these 14 candidates will help determine whether they are anti-stars or something more mundane, like a pulsar or a black hole.

The research has been published in Physical Review D.

[Airbrush]

Would anyone care to try to explain how "anti-stars" could form?  Antimatter could be so isolated that the majority of matter in a region of the universe could form stars?  But in the early universe, matter and antimatter could not be isolated, so they would annihilate.  For that reason it is hard to imagine how a star could form from antimatter. 

Edited May 4, 2021 by Airbrush

[MigL]

I think anti-matter stars is jumping the gun.
There are many other viable explanations.

[swansont]

The phrasing of the abstract is that these sources can’t be ruled out, which is quite different from claiming positive evidence that they are anti-stars

[beecee]

Leaning on swansont's correct scientific statement above, could anti matter exist as BH's? Which prompts me to ask if we throw the same amount of anti matter inside a baryonic matter BH, would they both disappear in a flash of gamma radiation?

Other then being of opposite charges, are we sure that this is all that distinguishes matter from anti matter?

Another possible source is Dark Matter...at least according to this following reputable link......

https://www.nature.com/articles/d41586-019-03431-5

13 NOVEMBER 2019

Link between antimatter and dark matter probed:

Ultrasensitive experiments on trapped antiprotons provide a window onto possible differences between matter and antimatter. Now they could also shed light on the identity of dark matter — the ‘missing’ mass in the Universe.

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Mind boggling stuff and personally makes me wonder how and why so many people are critical of science!

[Halc]

7 hours ago, beecee said:

Leaning on swansont's correct scientific statement above, could anti matter exist as BH's? Which prompts me to ask if we throw the same amount of anti matter inside a baryonic matter BH, would they both disappear in a flash of gamma radiation?

Other then being of opposite charges, are we sure that this is all that distinguishes matter from anti matter?

Per the no-hair theorem, one can dump antimatter in a black hole with no different effect than dumping ordinary mass (or dark matter) into it.  It increases the mass and effects the angular momentum and charge accordingly, but no gamma reaction except for any interaction with say the accretion disk. This acts as sort of a long-term equalizer since any black hole will eventually radiate away with Hawking radiation, which emits no more matter than antimatter.

[beecee]

4 hours ago, Halc said:

Per the no-hair theorem, one can dump antimatter in a black hole with no different effect than dumping ordinary mass (or dark matter) into it.  It increases the mass and effects the angular momentum and charge accordingly, but no gamma reaction except for any interaction with say the accretion disk. This acts as sort of a long-term equalizer since any black hole will eventually radiate away with Hawking radiation, which emits no more matter than antimatter.

Ahh yeah, OK thanks for that...sort of counter intuitive the way I was looking at it, but makes sense. 

[Airbrush]

11 hours ago, Halc said:

Per the no-hair theorem, one can dump antimatter in a black hole with no different effect than dumping ordinary mass (or dark matter) into it.  It increases the mass and effects the angular momentum and charge accordingly, but no gamma reaction except for any interaction with say the accretion disk. This acts as sort of a long-term equalizer since any black hole will eventually radiate away with Hawking radiation, which emits no more matter than antimatter.

Then would you care to speculate on how an "anti-star" could form from a big region of antimatter dust and gas?  Suppose anti-stars DID exist, how did they form when in the early universe matter and antimatter were in close proximity?  How does a region of antimatter survive in an early dense universe that is majority matter?

Edited May 5, 2021 by Airbrush

[swansont]

Just now, Airbrush said:

Then would you care to speculate on how an "anti-star" could form from a big region of antimatter dust and gas? 

The same way normal stars form. The interactions are the same.

 

Just now, Airbrush said:

Suppose anti-stars DID exist, how did they form when in the early universe matter and antimatter were in close proximity?  How does a region of antimatter survive in an early universe that is majority matter?

Those are excellent questions. How, indeed?