<p>No, this visible glow cannot be due to matter-antimatter annihilation. As Peter Erwin mentions, electron-positron annihilation produces gamma-ray photons, (mostly) with the energy of 511 keV. Proton-antiproton (and neutron-antineutron) annihilation is <a href="https://physics.stackexchange.com/a/451337/123208">more complicated</a>, but it also results in gamma production, not visible light. I have some more details on hydrogen-antihydrogen collisions in my answer to <a href="https://physics.stackexchange.com/a/590085/123208">How can we detect antihydrogen?</a>.</p>
<p>When gamma radiation passes through matter, the matter is heated, primarily through <a href="https://en.wikipedia.org/wiki/Compton_scattering" rel="nofollow noreferrer">Compton scattering</a>. This can cause the matter to glow in the infrared and visible bands. However, it takes a <em>lot</em> of matter to cause significant absorption of gamma rays. The extremely tenuous gas of the solar wind and the dust present in the solar system may be warmed very slightly by astronomical gamma ray sources, but the proportion of cosmic gamma photons absorbed by that matter is negligible.</p>
<p>If there were some process creating gamma rays on the fringes of the solar system we'd expect to see a lot of gamma rays and perhaps a very tiny amount of infrared and visible light. But the survey by Rogier A. Windhorst et al finds a general glow of visible light, with no mention of an accompanying gamma ray component.</p>
<p>Cosmic gamma rays were first detected in the early 1970s, when the distinctive 511 keV radiation signature of electron-positron annihilation was detected coming from the centre of our galaxy. Since then, there have been numerous surveys of cosmic gamma ray sources, mostly investigating that central galactic source, but there have also been more general surveys, eg investigating the possible existence of regions in the universe where antimatter rather than matter is dominant.</p>
<p>There are several space telescopes that can detect gamma rays. The main one is <a href="https://en.wikipedia.org/wiki/INTEGRAL" rel="nofollow noreferrer">INTEGRAL</a>, launched on 17 October 2002. Its main instrument (IBIS) detects photons in the range 15 keV to 10 MeV. It has not reported a diffuse gamma ray glow coming from the outer regions of the solar system.</p>
<p>A paper that discusses cosmic gamma ray sources is</p>
<p><a href="https://www.aanda.org/articles/aa/abs/2005/38/aa2063-04/aa2063-04.html" rel="nofollow noreferrer">The all-sky distribution of 511 keV electron-positron annihilation emission</a>, by J. Knödlseder et al, A&amp;A 441, 513-532 (2005).<br />
DOI: 10.48550/arXiv.astro-ph/0506026</p>
<blockquote>
<p>We present a map of 511 keV electron-positron annihilation emission, based on data accumulated with the SPI spectrometer aboard ESA's INTEGRAL gamma-ray observatory, that covers approximately ~95% of the celestial sphere. Within the exposed sky area, 511 keV line emission is significantly detected towards the galactic bulge region and, at a very low level, from the galactic disk. </p>
</blockquote>
<p>And</p>
<p><a href="https://www.aanda.org/articles/aa/full_html/2011/07/aa16516-11/aa16516-11.html" rel="nofollow noreferrer">Searching for the 511 keV annihilation line from galactic compact objects with the IBIS gamma ray telescope</a> by G. De Cesare, A&amp;A 531, A56 (2011).<br />
DOI: 10.1051/0004-6361/201116516</p>
<blockquote>
<p>The first detection of a gamma ray line with an energy of about 500 keV from the center of our Galaxy dates back to the early seventies. Thanks to the astrophysical application of high spectral resolution detectors, it was soon clear that this radiation was due to the 511 keV photons generated by electron-positron annihilation. Even though the physical process are known, the astrophysical origin of this radiation is still a mystery.</p>
<p>[...]</p>
<p>We present the first deep IBIS 511 keV all-sky map, obtained by applying standard analysis to about 5 years of data. Possible 511 keV signals are also searched over hour-day-month timescales.</p>
</blockquote>
<p>Also see this more recent paper;</p>
<p><a href="https://iopscience.iop.org/article/10.3847/1538-4357/ab89a9" rel="nofollow noreferrer">Detection of the 511 keV Galactic Positron Annihilation Line with COSI</a>, by C. A. Kierans et al 2020, ApJ 895 44<br />
DOI: 10.3847/1538-4357/ab89a9</p>

CC BY-SA 4.0
2022-12-17T19:48:54.217Z
Thank you for your detailed answer, I definitely learned something from it, and I am sure it will probably teach others as well!
Jonathan
CC BY-SA 4.0
2022-12-17T19:59:23.683Z
@Jonathan My pleasure!
PM 2Ring
CC BY-SA 4.0
2022-12-15T14:19:29.073Z
2022-12-15T14:19:29.073Z
PM 2Ring
<p>Could the newly discovered glow in the solar system be a sparse cloud of interstellar antimatter slowly annihilating with the solar wind?
The glow I am talking about is discussed at: <a href="https://www.nasa.gov/feature/goddard/2022/hubble-detects-ghostly-glow-surrounding-our-solar-system" rel="noreferrer">https://www.nasa.gov/feature/goddard/2022/hubble-detects-ghostly-glow-surrounding-our-solar-system</a></p>
<p>I also wonder if this could be checked by looking for a corresponding gamma ray glow?</p>

CC BY-SA 4.0
2022-12-15T06:08:40.863Z
The paper is open access. [SKYSURF: Constraints on Zodiacal Light and Extragalactic Background Light through Panchromatic HST All-sky Surface-brightness Measurements. I. Survey Overview and Methods](https://iopscience.iop.org/article/10.3847/1538-3881/ac82af), Rogier A. Windhorst et al 2022 AJ 164 141, DOI [10.3847/1538-3881/ac82af](https://doi.org/10.3847/1538-3881/ac82af)
PM 2Ring
CC BY-SA 4.0
2022-12-15T06:27:17.250Z
Why would antimatter cause a visible glow?
PM 2Ring
CC BY-SA 4.0
2022-12-15T09:42:16.697Z
@ScienceAJ Electron-positron annihilation produces *gamma-ray* photons (of a very particular wavelength), not the optical-wavelength photons that are being reported.
Peter Erwin
CC BY-SA 4.0
2022-12-15T19:12:38.660Z
@ScienceAJ Since the reported observations are in the optical, X-ray and UV photons are not relevant (and I'd want to see a reference of some kind before I believed that electron-positron annihilation produces meaningful numbers of non-gamma-ray photons).
Peter Erwin
<solar-system><light><solar-wind><antimatter><gamma-rays>
Could the newly discovered glow in the solar system be antimatter?
Jonathan
# Could the newly discovered glow in the solar system be antimatter?

(Asked by: username_0 on 2022-12-15)

Could the newly discovered glow in the solar system be a sparse cloud of interstellar antimatter slowly annihilating with the solar wind?
The glow I am talking about is discussed at: <https://www.nasa.gov/feature/goddard/2022/hubble-detects-ghostly-glow-surrounding-our-solar-system>

I also wonder if this could be checked by looking for a corresponding gamma ray glow?

**Tags:** solar-system, light, solar-wind, antimatter, gamma-rays
> **Comments:**
> **username_1**: The paper is open access. [SKYSURF: Constraints on Zodiacal Light and Extragalactic Background Light through Panchromatic HST All-sky Surface-brightness Measurements. I. Survey Overview and Methods](https://iopscience.iop.org/article/10.3847/1538-3881/ac82af), Rogier A. Windhorst et al 2022 AJ 164 141, DOI [10.3847/1538-3881/ac82af](https://doi.org/10.3847/1538-3881/ac82af)  
> **username_1**: Why would antimatter cause a visible glow?  
> **username_2**: @ScienceAJ Electron-positron annihilation produces *gamma-ray* photons (of a very particular wavelength), not the optical-wavelength photons that are being reported.  
> **username_2**: @ScienceAJ Since the reported observations are in the optical, X-ray and UV photons are not relevant (and I'd want to see a reference of some kind before I believed that electron-positron annihilation produces meaningful numbers of non-gamma-ray photons).  

---

## 1 answers

### Answer by username_1 on 2022-12-15. Score: 3 | Accepted answer

No, this visible glow cannot be due to matter-antimatter annihilation. As Peter Erwin mentions, electron-positron annihilation produces gamma-ray photons, (mostly) with the energy of 511 keV. Proton-antiproton (and neutron-antineutron) annihilation is [more complicated](https://physics.stackexchange.com/a/451337/123208), but it also results in gamma production, not visible light. I have some more details on hydrogen-antihydrogen collisions in my answer to [How can we detect antihydrogen?](https://physics.stackexchange.com/a/590085/123208).

When gamma radiation passes through matter, the matter is heated, primarily through [Compton scattering](https://en.wikipedia.org/wiki/Compton_scattering). This can cause the matter to glow in the infrared and visible bands. However, it takes a *lot* of matter to cause significant absorption of gamma rays. The extremely tenuous gas of the solar wind and the dust present in the solar system may be warmed very slightly by astronomical gamma ray sources, but the proportion of cosmic gamma photons absorbed by that matter is negligible.

If there were some process creating gamma rays on the fringes of the solar system we'd expect to see a lot of gamma rays and perhaps a very tiny amount of infrared and visible light. But the survey by Rogier A. Windhorst et al finds a general glow of visible light, with no mention of an accompanying gamma ray component.

Cosmic gamma rays were first detected in the early 1970s, when the distinctive 511 keV radiation signature of electron-positron annihilation was detected coming from the centre of our galaxy. Since then, there have been numerous surveys of cosmic gamma ray sources, mostly investigating that central galactic source, but there have also been more general surveys, eg investigating the possible existence of regions in the universe where antimatter rather than matter is dominant.

There are several space telescopes that can detect gamma rays. The main one is [INTEGRAL](https://en.wikipedia.org/wiki/INTEGRAL), launched on 17 October 2002. Its main instrument (IBIS) detects photons in the range 15 keV to 10 MeV. It has not reported a diffuse gamma ray glow coming from the outer regions of the solar system.

A paper that discusses cosmic gamma ray sources is

[The all-sky distribution of 511 keV electron-positron annihilation emission](https://www.aanda.org/articles/aa/abs/2005/38/aa2063-04/aa2063-04.html), by J. Knödlseder et al, A&A 441, 513-532 (2005).  
DOI: 10.48550/arXiv.astro-ph/0506026

> We present a map of 511 keV electron-positron annihilation emission, based on data accumulated with the SPI spectrometer aboard ESA's INTEGRAL gamma-ray observatory, that covers approximately ~95% of the celestial sphere. Within the exposed sky area, 511 keV line emission is significantly detected towards the galactic bulge region and, at a very low level, from the galactic disk.

And

[Searching for the 511 keV annihilation line from galactic compact objects with the IBIS gamma ray telescope](https://www.aanda.org/articles/aa/full_html/2011/07/aa16516-11/aa16516-11.html) by G. De Cesare, A&A 531, A56 (2011).  
DOI: 10.1051/0004-6361/201116516

> The first detection of a gamma ray line with an energy of about 500 keV from the center of our Galaxy dates back to the early seventies. Thanks to the astrophysical application of high spectral resolution detectors, it was soon clear that this radiation was due to the 511 keV photons generated by electron-positron annihilation. Even though the physical process are known, the astrophysical origin of this radiation is still a mystery.
>
> [...]
>
> We present the first deep IBIS 511 keV all-sky map, obtained by applying standard analysis to about 5 years of data. Possible 511 keV signals are also searched over hour-day-month timescales.

Also see this more recent paper;

[Detection of the 511 keV Galactic Positron Annihilation Line with COSI](https://iopscience.iop.org/article/10.3847/1538-4357/ab89a9), by C. A. Kierans et al 2020, ApJ 895 44  
DOI: 10.3847/1538-4357/ab89a9

> **Comments:**
> **username_0**: Thank you for your detailed answer, I definitely learned something from it, and I am sure it will probably teach others as well!  
> **username_1**: @Jonathan My pleasure!  

---

