Post by Andrei Tchentchik on Aug 25, 2020 15:33:30 GMT 2
(.#493).- Antimatter in our Galaxy '2'.
Antimatter in our Galaxy '2'.
Richard Taillet
Teacher, Physical Researcher.
Published 07/01/2005 - Modified 10/28/2015.
Archives
A - The positrons
Our galaxy contains positrons, which we observe directly as antiprotons, but also indirectly, by the radiation they emit by annihilating with electrons. Indeed, this radiation has a well-determined energy (511 keV), which makes it very characteristic. We can thus map, in the sky, the quantity of positrons in the galaxy. The positrons cannot travel very far from the place where they are created (on the one hand because they are trapped by the magnetic fields, and on the other hand because they annihilate), and what one maps does not is not very far from the position of the positron sources.
The CGRO satellite, with the modules on board OSSE, EGRET, BATSE and COMPTEL.
Here are the maps of the intensity of this radiation of annihilation that we observed. On the left (click on it for the link to Astronomy Picture of the Day), the one that results from the analysis of 9 years of observations from the OSSE module (Oriented Scintillation Spectrometer Experiment) on the CGRO satellite. On the right, that coming from 6 months of observations of the SPI module on the INTEGRAL satellite.
Map of the distribution of electron-positron annihilation radiation in the galaxy, taken by OSSE
We see on the first image a large central point, two lateral arms (directed along the galactic plane) and a "vertical chimney". These growths have been much discussed. At first glance, one might think that the lateral arms are linked to the presence in the disc of radioactive elements by ß +. We will see right away that this is not the case. In fact, we are not going to comment much on this image, for the following reason: OSSE was not an imager, and the image presented here was obtained after a data processing probably too optimistic. Note that the image of OSSE seems, to the eye, finer than that of INTEGRAL, while the spatial resolution of the latter is actually much finer! The INTEGRAL satellite, with its much better spatial and spectral resolutions, observed only the central emission, and we will not focus the discussion on this point.
Image obtained by INTEGRAL. This map and the one above, are centered on the Galactic center, and are represented on the same scale.
The processes that lead to the emission of positrons in the Galaxy are again the same as those described in the previous pages: radioactive decays and high energy phenomena.
(Continued: (# 494) .- Antimatter in our Galaxy '2' Continued…).
F I N .
Antimatter in our Galaxy '2'.
Richard Taillet
Teacher, Physical Researcher.
Published 07/01/2005 - Modified 10/28/2015.
Archives
A - The positrons
Our galaxy contains positrons, which we observe directly as antiprotons, but also indirectly, by the radiation they emit by annihilating with electrons. Indeed, this radiation has a well-determined energy (511 keV), which makes it very characteristic. We can thus map, in the sky, the quantity of positrons in the galaxy. The positrons cannot travel very far from the place where they are created (on the one hand because they are trapped by the magnetic fields, and on the other hand because they annihilate), and what one maps does not is not very far from the position of the positron sources.
The CGRO satellite, with the modules on board OSSE, EGRET, BATSE and COMPTEL.
Here are the maps of the intensity of this radiation of annihilation that we observed. On the left (click on it for the link to Astronomy Picture of the Day), the one that results from the analysis of 9 years of observations from the OSSE module (Oriented Scintillation Spectrometer Experiment) on the CGRO satellite. On the right, that coming from 6 months of observations of the SPI module on the INTEGRAL satellite.
Map of the distribution of electron-positron annihilation radiation in the galaxy, taken by OSSE
We see on the first image a large central point, two lateral arms (directed along the galactic plane) and a "vertical chimney". These growths have been much discussed. At first glance, one might think that the lateral arms are linked to the presence in the disc of radioactive elements by ß +. We will see right away that this is not the case. In fact, we are not going to comment much on this image, for the following reason: OSSE was not an imager, and the image presented here was obtained after a data processing probably too optimistic. Note that the image of OSSE seems, to the eye, finer than that of INTEGRAL, while the spatial resolution of the latter is actually much finer! The INTEGRAL satellite, with its much better spatial and spectral resolutions, observed only the central emission, and we will not focus the discussion on this point.
Image obtained by INTEGRAL. This map and the one above, are centered on the Galactic center, and are represented on the same scale.
The processes that lead to the emission of positrons in the Galaxy are again the same as those described in the previous pages: radioactive decays and high energy phenomena.
(Continued: (# 494) .- Antimatter in our Galaxy '2' Continued…).
F I N .
