Post by Andrei Tchentchik on Aug 25, 2020 15:32:50 GMT 2
(.#492).- Antimatter in our Galaxy ‘1’ Continued…
Antimatter in our Galaxy ‘1’ Continued…
Richard Taillet
Teacher, Physical Researcher.
Published 07/01/2005 - Modified 10/28/2015.
Archives
B - Antiprotons and anti-nuclei
- Cosmic rays
Distribution of hydrogen in our Galaxy
The space between the stars is not entirely empty. There are gas (mainly hydrogen) of low density, and also very high energy particles, which constitute what are called cosmic rays. The composition of these cosmic rays is very rich, there are electrons and a wide variety of atomic nuclei. They also contain a small fraction of antiparticles, mainly antiprotons (1 antiproton per 10,000 protons approximately)! They are produced during the shocks between the particles of the cosmic rays and the nuclei of the interstellar gas (these shocks are called spallations), exactly in the same way as the particles of the cosmic rays can create antiparticles when they come to hit the gas which constitutes the atmosphere.
Zoom on a shock wave created by the interaction between the expanding envelope of a supernova and the interstellar gas at rest.
The interstellar medium being after all quite tenuous, these cosmic antiparticles can propagate long enough in the Galaxy without encountering matter, and travel several thousand light years. This explains why it is detected near the Earth or at the top of the atmosphere (for example by AMS and BESS, see above).
This antimatter component is fairly well understood. We know quite well the distribution of gases in the Galaxy, we also know quite well the distribution of cosmic rays in the Galaxy, and finally we know quite well the reactions that can occur during shocks. By gluing these three pieces, we can calculate the amount of antiprotons that should be present in the cosmic rays, and it turns out that when we do the measurement, we find a result quite compatible with what we had calculated.
It should also be noted that in addition to antiprotons, shock reactions can in principle create more complex nuclei, such as anti-deuterons (antineutron + antiproton), anti-helium nuclei, anti-carbon nuclei, etc. .. In practice, the probability of such an event decreases when we go to the heavier nuclei, and the only nuclei that this spallation process produces in appreciable quantity (which we can hope to detect) are the antiprotons and the antideuterons.
- Anti-stars
We said above that the Earth and its environment are essentially made up of matter ... What do we really know? The moon is made of matter too, otherwise the moon landing of the first lunar module would have given rise to a fantastic release of energy, starting with the vaporization of the astronauts ... The Sun is made of matter, these are particles that arrive to us , carried by the solar wind, and not antiparticles ... In fact, we have strong reasons to think that the stars which compose a Galaxy are all made of the same type of matter. If it were not the case, there would be reactions between the stellar wind emitted by the anti-stars and the interstellar gas, and one would detect the radiation resulting from these reactions. For the same reason, it is very likely that the galaxies of the same cluster are made of the same type of matter. This argument can be applied to all objects that are connected to others by gas.
However, it has been proposed that the Universe globally contains as much matter as antimatter (we will see later that this could be envisaged in certain cosmological scenarios). It would then be made up of large clusters of galaxies, and other clusters of anti-galaxies, which would be entirely made of anti-stars ...
On the left, a star; on the right an anti-star ...
The light coming from them would be exactly similar to that coming from the stars!
What would these anti-stars look like? They would be very similar to stars and we could not differentiate them from stars by their appearance. In fact, what we observe of stars and galaxies is the light they emit. Anti-stars would emit anti-photons ... which are the same particles as photons! They would therefore shine in the same way, and if the physics of antimatter is the same as the physics of matter, as current theories suggest, but also as recent experiments try to show (for example the ATHENA experiments and ATRAP mentioned above), then we cannot distinguish an anti-star from a star simply by observing them!
A very solid proof of the existence of anti-stars would be the detection of anti-helium nuclei, which would have been synthesized by a process similar to that which creates helium nuclei in ordinary stars, by fusion of antihydrogen, because we don't know of any other process efficient enough to create anti-helium. However, hope is slim, because it is likely that these anti-stars, if they exist, are in any case too far from us.
F I N .
Antimatter in our Galaxy ‘1’ Continued…
Richard Taillet
Teacher, Physical Researcher.
Published 07/01/2005 - Modified 10/28/2015.
Archives
B - Antiprotons and anti-nuclei
- Cosmic rays
Distribution of hydrogen in our Galaxy
The space between the stars is not entirely empty. There are gas (mainly hydrogen) of low density, and also very high energy particles, which constitute what are called cosmic rays. The composition of these cosmic rays is very rich, there are electrons and a wide variety of atomic nuclei. They also contain a small fraction of antiparticles, mainly antiprotons (1 antiproton per 10,000 protons approximately)! They are produced during the shocks between the particles of the cosmic rays and the nuclei of the interstellar gas (these shocks are called spallations), exactly in the same way as the particles of the cosmic rays can create antiparticles when they come to hit the gas which constitutes the atmosphere.
Zoom on a shock wave created by the interaction between the expanding envelope of a supernova and the interstellar gas at rest.
The interstellar medium being after all quite tenuous, these cosmic antiparticles can propagate long enough in the Galaxy without encountering matter, and travel several thousand light years. This explains why it is detected near the Earth or at the top of the atmosphere (for example by AMS and BESS, see above).
This antimatter component is fairly well understood. We know quite well the distribution of gases in the Galaxy, we also know quite well the distribution of cosmic rays in the Galaxy, and finally we know quite well the reactions that can occur during shocks. By gluing these three pieces, we can calculate the amount of antiprotons that should be present in the cosmic rays, and it turns out that when we do the measurement, we find a result quite compatible with what we had calculated.
It should also be noted that in addition to antiprotons, shock reactions can in principle create more complex nuclei, such as anti-deuterons (antineutron + antiproton), anti-helium nuclei, anti-carbon nuclei, etc. .. In practice, the probability of such an event decreases when we go to the heavier nuclei, and the only nuclei that this spallation process produces in appreciable quantity (which we can hope to detect) are the antiprotons and the antideuterons.
- Anti-stars
We said above that the Earth and its environment are essentially made up of matter ... What do we really know? The moon is made of matter too, otherwise the moon landing of the first lunar module would have given rise to a fantastic release of energy, starting with the vaporization of the astronauts ... The Sun is made of matter, these are particles that arrive to us , carried by the solar wind, and not antiparticles ... In fact, we have strong reasons to think that the stars which compose a Galaxy are all made of the same type of matter. If it were not the case, there would be reactions between the stellar wind emitted by the anti-stars and the interstellar gas, and one would detect the radiation resulting from these reactions. For the same reason, it is very likely that the galaxies of the same cluster are made of the same type of matter. This argument can be applied to all objects that are connected to others by gas.
However, it has been proposed that the Universe globally contains as much matter as antimatter (we will see later that this could be envisaged in certain cosmological scenarios). It would then be made up of large clusters of galaxies, and other clusters of anti-galaxies, which would be entirely made of anti-stars ...
On the left, a star; on the right an anti-star ...
The light coming from them would be exactly similar to that coming from the stars!
What would these anti-stars look like? They would be very similar to stars and we could not differentiate them from stars by their appearance. In fact, what we observe of stars and galaxies is the light they emit. Anti-stars would emit anti-photons ... which are the same particles as photons! They would therefore shine in the same way, and if the physics of antimatter is the same as the physics of matter, as current theories suggest, but also as recent experiments try to show (for example the ATHENA experiments and ATRAP mentioned above), then we cannot distinguish an anti-star from a star simply by observing them!
A very solid proof of the existence of anti-stars would be the detection of anti-helium nuclei, which would have been synthesized by a process similar to that which creates helium nuclei in ordinary stars, by fusion of antihydrogen, because we don't know of any other process efficient enough to create anti-helium. However, hope is slim, because it is likely that these anti-stars, if they exist, are in any case too far from us.
F I N .
