# Radiation astronomy/Subatomics

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This is an image obtained from muon radiography of Japan's Asama volcano. Credit: H T M Tanaka.

Subatomic astronomy is an observational astronomy using one or more subatomic particles or radiation.

A variety of subatomic particle astronomies have already been developed. These are highlighted below.

Potential particle astronomies are examined for their likelihood of becoming a successful astronomy.

## Theoretical subatomic astronomy

The bare nuclei of atoms may qualify as a form of subatomic astronomy.

Def. "particles that are constituents of the atom, or are smaller than an atom; such as proton, neutron, electron, etc"[1] or "any length or mass that is smaller in scale than a the diameter of a hydrogen atom"[1]

are called subatomics, or subatomic, respectively.

As a bare uranium nucleus is smaller than a hydrogen atom in diameter, but much larger in mass, it qualifies as one of the subatomics. Here, subatomic is used to mean smaller than the diameter of a hydrogen atom.

A neutron star is one nucleus surrounded by an electron cloud. But, it is much larger than a hydrogen atom in diameter.

## Cosmic rays

About 89% of cosmic rays are simple protons or hydrogen nuclei, 10% are helium nuclei or alpha particles, and 1% are the nuclei of heavier elements. Solitary electrons constitute much of the remaining 1%.

In cosmic-ray astronomy, cosmic rays are not charge balanced; that is, positive ions heavily outnumber electrons.

## Anomalous cosmic rays

A mechanism is suggested for anomalous cosmic rays (ACRs) of the acceleration of pick-up ions at the solar wind termination shock. Credit: Eric R. Christian.{{fairuse}}

"While interstellar plasma is kept outside the heliosphere by an interplanetary magnetic field, the interstellar neutral gas flows through the solar system like an interstellar wind, at a speed of 25 km/sec. When closer to the Sun, these atoms undergo the loss of one electron in photo-ionization or by charge exchange. Photo-ionization is when an electron is knocked off by a solar ultra-violet photon, and charge exchange involves giving up an electron to an ionized solar wind atom. Once these particles are charged, the Sun's magnetic field picks them up and carries them outward to the solar wind termination shock. They are called pickup ions during this part of their trip."[2]

"The ions repeatedly collide with the termination shock, gaining energy in the process. This continues until they escape from the shock and diffuse toward the inner heliosphere. Those that are accelerated are then known as anomalous cosmic rays."[2]

"ACRs [may] represent a sample of the very local interstellar medium. They are not thought to have experienced such violent processes as GCRs, and they have a lower speed and energy. ACRs include large quantities of helium, oxygen, neon, and other elements with high ionization potentials, that is, they require a great deal of energy to ionize, or form ions. ACRs are a tool for studying the movement of energetic particles within the solar system, for learning the general properties of the heliosphere, and for studying the nature of interstellar material itself."[2]

## Solar energetic particles

Mean Fe charge states as a function of energy for the same event (in red) with overall mean charge state and test result for null-hypothesis (i.e. random distribution around mean). Credit: Zhangbo Guo, Eberhard Moebius, and Mark Popecki.{{fairuse}}
Charge state of Fe is a function of energy for an impulsive event in September 2000 in comparison with that for a CME-related event in June 1999 and the charge state of adjacent solar wind. Credit: Berndt Klecker and Eberhard Moebius.{{fairuse}}

"Earlier observations with ACE/SEPICA, SAMPEX/LICA, and SOHO/STOF have shown that highly ionized Fe in solar energetic particle (SEP) events (mean QFe > 14) is usually coupled with an increase of the mean charge state with energy in the range from 0.01 to 1 MeV/amu [...]. At the lowest energies the mean charge state of Fe is typically found to be well below QFe = 14. Recently, this has been demonstrated for all impulsive SEP events that were observed with SEPICA (DiFabio et al., ApJ, Nov 2008), indicating that the greater degree of ionization at higher energies was established by electron stripping in the low corona (e.g. Kartavykh et al., ApJ, 671, 947, 2007). However, observations of solar wind charge states have shown a widespread presence of QFe ≥ 16, associated with a hot plasma environment in solar wind from active regions and in interplanetary [Coronal Mass Ejections] CMEs (e.g. Lepri et al., JGR, 106, 29231, 2001; ACE News #52)."[3]

"Mean Fe charge states [in the figure on the right are] a function of energy for the same event (in red) with overall mean charge state and test result for null-hypothesis (i.e. random distribution around mean). Shown for comparison is an impulsive [Solar Energetic Particle] SEP event from June 2000 (in blue)."[3]

"Impulsive solar energetic particle events are well known for their dramatic over-abundances in 3He and heavy ions. ACE observations have extended these composition peculiarities to overabundances in the heavy isotopes of Ne and Mg."[4]

"The first charge-state measurements of impulsive events, averaged over all such events observed during one year with ISEE ULEZEQ, suggested that impulsive events feature rather high charge states with Q ≈ 20 for Fe and all elements up to Mg essentially fully stripped. These high charge states appeared to be well separated from the group of large, CME-related events with Q ≈ 14 for Fe."[4]

"With ACE SEPICA we have found that solar energetic particle events generally show a wide variety of mean charge states for Fe ranging from Q ≈ 10 continuously up to Q ≈ 20. Also, element abundance ratios appear to correlate with the ionic charge states (see ACE News #33). These two results seemed to present a puzzle, as the highest overabundances of heavy ions were observed for events with essentially fully-ionized ions up to Mg, which would not lend itself to an M/Q-based explanation for the observed fractionation. Therefore, it was suggested that fractionation and acceleration occur among lower charge state ions, with the final high charge states attained through stripping. This idea appears to be corroborated now by the observation of a very strong energy dependence of the iron charge states from 0.2 to 0.5 MeV/nuc with ACE SEPICA, a pattern that is even more pronounced when extended to ~0.01 MeV/nuc with the SOHO CELIAS STOF instrument."[4]

The "charge state of Fe [in the second figure down on the right is] a function of energy for an impulsive event in September 2000 in comparison with that for a CME-related event in June 1999 and the charge state of adjacent solar wind. Whereas the CME-related event shows Q ≈ 10 over the entire energy range, commensurate with that of the solar wind, in the impulsive event the charge state increases from Q ≈ 12 at low energies up to Q ≈ 17 at 0.5 MeV/nuc. This observation suggests that the original source material which is accelerated in these events has a much lower temperature than previously thought and is only partially ionized, thereby lending itself to M/Q fractionation. The sharp increase of the charge state with energy can be explained by electron stripping that increases with energy. This also implies that the acceleration in impulsive events occurs in the lower corona."[4]

## Ultra-heavy element nuclei

Absolute flux Φ0Z of cosmic–ray elements at E0 = 1 TeV/nucleus is plotted versus nuclear charge. Credit: Jörg R. Hörandel.{{fairuse}}

"The iron group and the ultra–heavy elements are more pronounced in cosmic rays as compared to the solar system. Especially the r–process elements beyond xenon (Z=54) are enhanced, partly due to spallation products of the platinum and lead nuclei (Z=78, 82). For the latter direct measurements at low energies around 1 GeV/n yield about a factor two more abundance as compared to the solar system and a factor of four for the actinides thorium and uranium (Z=90, 92) [66]. This has been attributed to the hypothesis that cosmic rays are accelerated out of supernova ejecta–enriched matter [67]."[5]

## Heavier element nuclei

The distribution of galactic cosmic-ray (GCR) particles is shown in atomic number (charge) and energy. Credit: W. Schimmerling, J. W. Wilson, F. Cucinotta, and M-H Y. Kim.{{fairuse}}

"These charged particles are hydrogen nuclei (protons), helium nuclei (α particles), and the nuclei of heavier elements such as iron and nickel."[6]

"Primary cosmic radiation mainly consists of the nuclei of atoms which have lost their electrons due to their extremely high velocity; these charged particles are hydrogen nuclei (protons), helium nuclei (alpha particles) and the nuclei of heavier elements such as iron and nickel; there are also some electrons (1%) and positrons (1‰)."[6]

"The relative abundances of GCR particles (9) are shown in [the figure on the right] (a), and typical energy spectra (10), are shown in [...] (b). The GCR particles of interest for radiation protection of crews engaged in space exploration range from protons (nuclei of hydrogen) to nuclei of iron; the abundances of heavier elements are orders of magnitude lower."[7]

Heavier element nuclei consist primarily of Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co and Ni.

"The two groups of elements Li, Be, B and Sc, Ti, V, Cr, Mn are many orders of magnitude more abundant in the cosmic radiation than in solar system material."[8]

## Neon nuclei

The ACE-CRIS measurements of the ratios 22Ne/20Ne and 21Ne/20Ne are plotted as a function of energy. Credit: W.R. Binns, M.E. Wiedenbeck, M. Arnould, A.C. Cummings, J.S. George, S. Goriely, M.H. Israel, R.A. Leske, R.A. Mewaldt, G. Meynet, L. M. Scott, E.C. Stone, and T.T. von Rosenvinge.{{fairuse}}

On the right, "the ACE-CRIS measurements of the ratios 22Ne/20Ne and 21Ne/20Ne are plotted as a function of energy. Abundances measured by other experiments (Wiedenbeck & Greiner 1981 [ISEE-3]; Lukasiak et al. 1994 [Voyager]; Connell & Simpson 1997 [Ulysses]; DuVernois et al. 1996 [CRRES]) are plotted as open symbols and the energy intervals for their measurements are shown as horizontal bars at the bottom of the figure."[9]

## Oxygen nuclei

Oxygen fluences were observed by the Advanced Composition Explorer (ACE). Credit: Richard Mewaldt, Caltech.

The fluences of oxygens in the galactic cosmic rays (GCRs) are plotted on the graph at right using data from the Cosmic Ray Isotope Spectrometer (CRIS) aboard the Advanced Composition Explorer (ACE). The fluences of solar 'cosmic rays' add to the GCRs at lower energy.

## Nitrogen nuclei

"For cosmic rays the low abundance ”valleys” in the solar system composition around Z=4, 21, 46, and 70 are not present. This is usually believed to be the result of spallation of heavier nuclei during their propagation through the galaxy. Hydrogen, helium, and the CNO–group are suppressed in cosmic rays. This has been explained by the high first ionization potential of these atoms [63] or by the high volatility of these elements which do not condense on interstellar grains [64]. Which property is the right descriptor of cosmic–ray abundances has proved elusive, however, the volatility seems to become the more accepted solution [65]."[5]

## Carbon nuclei

These "are nevertheless present in the cosmic radiation as spallation products of the abundant nuclei of carbon and oxygen (Li,Be,B) and of iron (Sc,Ti,V,Cr,Mn)."[8]

## Boron nuclei

Absolute boron and carbon fluxes multiplied by E2.7 as measured by PAMELA. Credit: O. Adriani, G. C. Barbarino, G. A. Bazilevskaya, R. Bellotti, M. Boezio, E. A. Bogomolov, M. Bongi, V. Bonvicini, S. Bottai, A. Bruno, F. Cafagna, D. Campana, R. Carbone, P. Carlson, M. Casolino, G. Castellini, I. A. Danilchenko, C. De Donato1, C. De Santis, N. De Simone, V. Di Felice, V. Formato, A. M. Galper, A. V. Karelin, S. V. Koldashov, S. Koldobskiy, S. Y. Krutkov, A. N. Kvashnin, A. Leonov, V. Malakhov, L. Marcelli, M. Martucci, A. G. Mayorov, W. Menn, M. Mergé, V. V. Mikhailov, E. Mocchiutti, A. Monaco, N. Mori, R. Munini, G. Osteria, F. Palma, B. Panico, P. Papini, M. Pearce, P. Picozza, C. Pizzolotto, M. Ricci, S. B. Ricciarini, L. Rossetto, R. Sarkar, V. Scotti, M. Simon, R. Sparvoli, P. Spillantini, Y. I. Stozhkov, A. Vacchi, E. Vannuccini, G. I. Vasilyev, S. A. Voronov, Y. T. Yurkin, G. Zampa, N. Zampa, and V. G. Zverev.{{fairuse}}

"In cosmic rays, both the isotopes 10B and 11B are present in comparable quantities."[10]

In the figure on the right are absolute boron and carbon fluxes multiplied by E2.7 as measured by PAMELA, together with results from other experiments (AMS02 Oliva et al. (2013), CREAM Ahn et al. (2008), TRACER Obermeier et al. (2011), ATIC-2 Panov et al. (2007), HEAO Engelmann et al. (1990), AMS01 Aguilar et al. (2010), CRN Swordy et al. (1990)) and a theoretical calculation based on GALPROP, as functions of kinetic energy per nucleon.

## Berylliums

The "presence in ... cosmic radiation [is] of a much greater proportion of "secondary" nuclei, such as lithium, beryllium and boron, than is found generally in the universe."[8]

## Lithium nuclei

The "evidence for the overwhelming majority of the Li-atoms in photospheres has its origin not only in nuclear synthesis near the stellar centers, but also by active processes in stellar atmospheres. [...] the lithium [resonance] line [is] near 478 keV."[11]

"Approximately 90% of lithium atoms originate from α - α reactions for the typical spectra of an accelerated particles on the Sun [...] During impulsive flares, interaction between the accelerated particles and the ambient medium occurs mainly at low altitudes, i.e., close to the footprints of loops."[11]

## Alpha particles

About 89% of cosmic rays are simple protons or hydrogen nuclei, 10% are helium nuclei or alpha particles, and 1% are the nuclei of heavier elements. Solitary electrons constitute much of the remaining 1%.

## Helions

Def. a "nucleus of a helium-3 atom"[12] is called a helion.

## Tritons

Energetic deuterons and tritons have been detected in solar flares.[13]

## Deuterons

"The flux [of deuterons in cosmic rays at a geomagnetic latitude of 7.6°N] is found to be 4 ± 1.3 M-2 sec-1 sterad-1".[14]

## Baryons

In "dense nuclear matter, such as neutron stars [it] has recently been discovered that kaon condensation in nuclear matter at a density of a few times normal nuclear matter may significantly reduce the upper mass limit of neutron stars [...] This clearly has an impact on astronomical observations. By exploiting the electron fermi level, we are able to predict kaon production at reasonable baryon number densities [...] Experimental detection of [dibaryons, hyperons] is a subtle matter [...] there is strong theoretical evidence that such states [as the dibaryon] do exist in nature. [...] the lightest dibaryon [...] is energetically stable against strong decay to [ΛΛ baryons] by 88 MeV. [The H dibaryon] is bound by 250 MeV."[15]

## Neutrons

The neutron probe is in the hole on the Moon. Credit: NASA.

Neutron astronomy deals with the study of astronomical neutron sources (such as stars, planets, comets, nebulae, star clusters and galaxies and phenomena that originate outside the Earth's atmosphere, such as cosmic rays.

## Protons

The diagram shows one of the Van Allen Probes with various components and subsystems labeled. Credit: JHU/APL.

Proton astronomy per se often consists of directly or indirectly detecting the protons and deconvoluting a spatial, temporal, and spectral distribution.

"Proton astronomy should be possible; it may also provide indirect information on inter-galactic magnetic fields."[16]

"The Relativistic Proton Spectrometer (RPS) [measures] inner radiation belt protons with energies from 50 MeV-2 GeV. Such protons are known to pose a number of hazards to humans and spacecraft, including total ionizing dose, displacement damage, single event effects, and nuclear activation. The objectives of the investigation are to: (1) support the development of a new AP9/AE9 standard radiation model for spacecraft design; (2) to develop and test the model for RBSP data in general and RPS specifically; and, (3) to provide standardized worst-case specifications for dose rate, internal and deep dielectric chargins, and surface charging."[17]

## Mesons

Mesons are hadronic subatomic particles, bound together by the strong interaction. Because mesons are composed of sub-particles, they have a physical size, with a radius roughly one femtometre, which is about 23 the size of a proton or neutron.

Charged mesons decay (sometimes through intermediate particles) to form electrons and neutrinos. Uncharged mesons may decay to photons.

Mesons are not produced by radioactive decay, but appear in nature only as short-lived products of very high-energy interactions in matter. In cosmic ray interactions, for example, such particles are ordinary protons and neutrons. Mesons are also frequently produced artificially in high-energy particle accelerators that collide protons, anti-protons, or other particles.

Mesons are subject to both the weak and strong interactions. Mesons with net electric charge also participate in the electromagnetic interaction.

While no meson is stable, those of lower mass are nonetheless more stable than the most massive mesons, and are easier to observe and study in particle accelerators or in cosmic ray experiments. They are also typically less massive than baryons, meaning that they are more easily produced in experiments, and thus exhibit certain higher energy phenomena more readily than baryons composed of the same quarks would.

Potential mesons to be detected astronomically include: π, ρ, η, η′, φ, ω, J/ψ, ϒ, θ, K, B, D, and T.

## B mesons

"The K0-K0 bar, D0-D0 bar, and B0-B0 bar oscillations are extremely sensitive to the K0 and K0 bar energy at rest. The energy is determined by the values mc2 with the related mass as well as the energy of the gravitational interaction. Assuming the CPT theorem for the inertial masses and estimating the gravitational potential through the dominant contribution of the gravitational potential of our Galaxy center, we obtain from the experimental data on the K0-K0 bar oscillations the following constraint: |(mg/mi)K0 - (mg/mi)K0 bar| ≤ 8·10-13, CL=90%. This estimation is model dependent and in particular it depends on a way we estimate the gravitational potential. Examining the K0-K0 bar, B0-B0 bar, and D0-D0 bar oscillations provides us also with weaker, but model independent constraints, which in particular rule out the very possibility of antigravity for antimatter."[18]

## Upsilon mesons

A plot of the invariant mass of muon pairs, the peak at about 9.5 GeV is due to the contribution of the Upsilon meson. Credit: Leon Lederman and the E288 collaboration, Fermilab.

The plot on the right shows a peak at about 9.5 GeV due to the Upsilon meson.

## Psions

J/Ψ production is graphed. Credit: Fermilab.

On the right is a graph of the production of psions at Fermilab.

## Omega mesons

Omega meson production:[19]

1. ${\displaystyle p+d\rightarrow He^{3}+\omega ,}$
2. ${\displaystyle {\bar {p}}+p\rightarrow \omega +\eta +\pi _{0},}$
3. ${\displaystyle \pi ^{-}+p\rightarrow \omega +n,}$
4. ${\displaystyle p+{\bar {p}}\rightarrow \mathrm {K} ^{+}+\mathrm {K} ^{-}+\omega ,}$
5. ${\displaystyle p+{\bar {p}}\rightarrow \mathrm {K} 1+\mathrm {K} 1+\omega ,}$

## Phi mesons

The phi meson ${\displaystyle \Phi ^{0}}$(1020) has a mass of 1019.445 MeV. It decays per[20]

1. ${\displaystyle \Phi ^{0}\rightarrow \mathrm {K} ^{+}+\mathrm {K} ^{-}or}$
2. ${\displaystyle \Phi ^{0}\rightarrow \mathrm {K} _{S}^{0}+\mathrm {K} _{L}^{0}.}$

## Rho mesons

Rho mesons occur in three states: ρ+, ρ-, and ρ0.[20] The rest masses are apparently the same at 775.4±0.4 and 775.49±0.34.[20] Decay products are π± + π0 or π+ + π-, respectively.[20]

## Eta mesons

Eta mesons (547.863 ± 0.018 MeV) have the decay schemes:[19]

1. η : ${\displaystyle \eta \rightarrow \gamma +\gamma ,}$
2. η : ${\displaystyle \eta \rightarrow \pi ^{0}+\pi ^{0}+\pi ^{0},or}$
3. η : ${\displaystyle \eta \rightarrow \pi ^{+}+\pi ^{0}+\pi ^{-},}$

Eta prime mesons (957.78 ± 0.06 MeV) have the decay schemes:[19]

1. η' : ${\displaystyle \eta ^{'}\rightarrow \pi ^{+}+\pi ^{-}+\eta or}$
2. η' : ${\displaystyle \eta ^{'}\rightarrow \pi ^{0}+\pi ^{0}+\gamma ,}$

The charmed eta meson ηC(1S) has a rest mass of 2983.6 ± 0.7 MeV.[19]

## D mesons

${\displaystyle D_{S}\rightarrow \tau +{\bar {\nu }}_{\tau }\rightarrow \nu _{\tau }+{\bar {\nu }}_{\tau }.}$[21]

## Kaons

"The muons created through decays of secondary pions and kaons are fully polarized, which results in electron/positron decay asymmetry, which in turn causes a difference in their production spectra."[22]

The "highest energy neutrinos from GRBs mainly come from kaons."[23]

## Pions

"The Gamma-Ray Spectrometer (GRS) on [Solar Maximum Mission] SMM has detected [...] at least two of the flares have spectral properties >40 MeV that require gamma rays from the decay of neutral pions. [Pion] production can occur early in the impulsive phase as defined by hard X-rays near 100 keV."[24]

## Tauons

"For ultrahigh energies the neutrino spectrum at the detector is influenced by neutrino-nucleon interactions and tauon decays during the passage through the interior of the earth."[25]

## Muons

The Moon's cosmic ray shadow, as seen in secondary muons generated by cosmic rays in the atmosphere, and detected 700 meters below ground, at the Soudan II detector. Credit: Deglr6328.

"TeV muons from γ ray primaries ... are rare because they are only produced by higher energy γ rays whose flux is suppressed by the decreasing flux at the source and by absorption on interstellar light."[26]

"[T]here is a window of opportunity for muon astronomy with the AMANDA, Lake Baikal, and MILAGRO detectors."[26]

## Neutrinos

The diagram contains the reactions in the proton-proton chain including neutrino production. Credit: Dorottya Szam.

The highest flux of solar neutrinos come directly from the proton-proton interaction, and have a low energy, up to 400 keV. There are also several other significant production mechanisms, with energies up to 18 MeV. [27]

## Beta particles

This graph is a chart of the nuclides for carbon to fluorine. Decay modes:

Credit: original: National Nuclear Data Center, stitched: Neokortex, cropped: Limulus.

Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. The beta particles emitted are a form of ionizing radiation also known as beta rays. The production of beta particles is termed beta decay. They are designated by the Greek letter beta (β).

At right is a graph or block diagram that shows the boundaries for nuclear particle stability. The boundaries are conceptualized as drip lines. The nuclear landscape is understood by plotting boxes, each of which represents a unique nuclear species, on a graph with the number of neutrons increasing on the abscissa and number of protons increasing along the ordinate, which is commonly referred to as the table of nuclides, being to nuclear physics what the more commonly known periodic table of the elements is to chemistry. However, an arbitrary combination of protons and neutrons does not necessarily yield a stable nucleus, and ultimately when continuing to add more of the same type of nucleons to a given nucleus, the newly formed nucleus will essentially undergo immediate decay where a nucleon of the same isospin quantum number (proton or neutron) is emitted; colloquially the nucleon has 'leaked' or 'dripped' out of the target nucleus, hence giving rise to the term "drip line". The nucleons drip out of such unstable nuclei for the same reason that water drips from a leaking faucet: the droplet, or nucleon in this case, sees a lower potential which is great enough to overcome surface tension in the case of water droplets, and the strong nuclear force in the case of proton emission or alpha decay. As nucleons are quantized, then only integer values are plotted on the table of isotopes, indicating that the drip line is not linear but instead looks like a step function up close.

Beta particles (electrons) are more penetrating than alpha particles, but still can be absorbed by a few millimeters of aluminum. However, in cases where high energy beta particles are emitted shielding must be accomplished with low density materials, e.g. plastic, wood, water or acrylic glass (Plexiglas, Lucite). This is to reduce generation of Bremsstrahlung X-rays. In the case of beta+ radiation (positrons), the gamma radiation from the electron-positron annihilation reaction poses additional concern.

As an example, "[t]he power into the Crab Nebula is apparently supplied by an outflow [wind] of ~1038 erg/s from the pulsar"[28] where there are "electrons (and positrons) in such a wind"[28]. These beta particles coming out of the pulsar are moving very close to light speed.

## Electrons

Beam of electrons are moving in a circle in a magnetic field (cyclotron motion). Lighting is caused by excitation of atoms of gas in a bulb. Credit: Marcin Białek.

Although electron astronomy is usually not recognized as a formal branch of astronomy, the measurement of electron fluxes helps to understand a variety of natural phenomena.

""[E]lectron astronomy" has an interesting future".[29]

"Electron beams can be generated by thermionic emission, field emission or the anodic arc method. The generated electron beam is accelerated to a high kinetic energy and focused towards the [target]. When the accelerating voltage is between 20 kV – 25 kV and the beam current is a few amperes, 85% of the kinetic energy of the electrons is converted into thermal energy as the beam bombards the surface of the [target]. The surface temperature of the [target] increases resulting in the formation of a liquid melt. Although some of incident electron energy is lost in the excitation of X-rays and secondary emission, the [target] material evaporates under vacuum."[30]

## Positrons

Positron astronomy results have been obtained using the INTEGRAL spectrometer SPI shown. Credit: Medialab, ESA.

"Positron astronomy is 30 years old but remains in its infancy."[31]

In 2009, the Fermi Gamma Ray Telescope in Earth orbit observed an intense burst of gamma rays corresponding to positron annihilations coming out of a storm formation. Scientists wouldn't have been surprised to see a few positrons accompanying any intense gamma ray burst, but the lightning flash detected by Fermi appeared to have produced about 100 trillion positrons. This has been reported by media in January 2011, it is an effect, never considered to happen before.[32]

## Hypotheses

1. Each extant subatomic particle may help to understand a radiation source.

## References

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