Simple Explanation for Mysterious Observations

August 18, 2009

Recently, several astronomical experiments have revealed mysterious components of elementary particles. But up until now, the origin of electrons and positrons is unknown. Is dark matter the actual origin of this radiation, as some physicists speculate?

Now an international team of astrophysicists, including the Bochum junior professor Dr. Julia Becker and the Dortmund physicist Prof. Dr. Dr. Wolfgang Rohde, have found a simple explanation: giant stars, at least fifteen times the mass of our sun, emit elementary particles in a final explosion when they die. The flux of the electrons and positrons calculated on the basis of this theory fits in with the enigmatic signals observed during these astronomical experiments. The six-strong team of international scientists outlines how their theory of supernova explosions explains the observations in the latest edition of Physical Review Letters (printed edition on August 7th 2009).

Elementary Particles from the Universe

In connection with various astronomical experiments there have been reports about the observation of mysterious components of electrons and positrons from the universe. The sources of these cannot be identified by the experiments alone: cosmic magnetic fields deflect them from their path and cover their tracks. Since these findings were published, there have been several attempts to explain the origin of this particle radiation. Among others, the theory has been put forward that such a signal can only be explained by the so-called dark matter - a kind of matter whose origin is not absolutely clear yet. “But maybe nature can offer a much simpler explanation for the observed particles” says Julia Becker, who is cooperating with a research team with members from institutes in Germany, the USA and Sweden. The team explains the particle radiation with explosions of giant stars with at least fifteen times the mass of the sun.

The Dramatic Death of Giant Stars

A with a high mass catapults most of its matter, called plasma, in a final explosion into the universe. The result is that the ejected plasma inevitably collides with the matter surrounding the star - the so-called stellar wind. It builds up around massive stars as they lose part of their shell before dying in a final explosion. “During the collision between fast matter from this final explosion and plasma from previous ejections a shock front is formed, similar to the ones that can be observed in case of supersonic aircrafts”, explains the Dortmund astrophysicist Wolfgang Rhode. “When an aircraft flies faster than the sound, the air surrounding the plane is pushed aside with a speed that exceeds sonic speed. A sonic bang occurs, which spreads in the form of a shock front.”  The shock front is the point of discontinuous change in density of the medium itself - where the aircraft pushes away the matter the density becomes very high. On the other side of the shock there is the low density of an undisturbed atmosphere. Exactly the same happens when plasma with a high velocity is pushed into slower plasma, as is the case with the giant stars.

Electrons and Positrons Resulting from Supernova Explosions

How electrons and positrons are accelerated in shock fronts of supernova explosions is explained by the scientists in their article: as the plasma blazes its trail through the stellar wind, two different regions emerge with different shockwaves forming in each region. The magnetic fields of the star are aligned vertically to the velocity of the shock front on almost the whole surface. Here a low-energy signal from the electrons and positrons emerges. At the same time the at the poles of the once rotating star is aligned parallel to the velocity of the shockwave. As a result ultrahigh-energy electron radiation is produced. Both components are visible in the observed spectrum of electrons and positrons and the measurements can be explained by the model of the research team. “This means that dark matter this means that it does not produce electrons and positrons in the same amount as giant stars and that one has to look for evidence of elsewhere” concludes Dr. Becker.

More information: Peter L. Biermann, Julia K. Becker, A. Meli, W. Rhode, E.-S. Seo and T. Stanev: Cosmic Ray Electrons and Positrons from Supernova Explosions of Massive Stars. In: , PRL 103, 061101 (2009), DOI: 10.1103/PhysRevLett.103.061101

Source: Technische Universitaet Dortmund

Explore further: Particles as tracers for the most massive explosions in the Milky Way

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3.7 / 5 (3) Aug 18, 2009
Here comes Zephir in 5...... 4...... 3...... 2......
Aug 18, 2009
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3 / 5 (4) Aug 18, 2009
The separation of particles and antiparticles from jets of supernovas and black holes can be explained in illustrative way by process of adiabatic cooling. We can imagine the hot mixture of matter and antimatter like hot gas above candle. When we cool such gas (by inserting of teaspoon, for example or simply by cooling of flame by cold wind) we can reach the separation of thermodynamically unstable mixture of original components, i.e. carbon from soot and oxygen gas.


Another example is the formation of Wilson cloud during strong adiabatic cooling of compressed wet gas during explosions and supersonic boom. The mixture of water droplets and dry air is thermodynamically unstable, but it can still be formed, if we release pressure suddenly, thus separating both components. The same process (i.e. separation of matter and antimatter) could occur during inflationary phase of Universe formation under collision of black holes. Dark matter streaks and observable matter are remnants of Wilson cloud formed during Universe condensation and we can reconcile ekyrotic cosmology with inflation in such a way.

3 / 5 (4) Aug 18, 2009
A little bit more detailed insight we can get, if we consider dynamic equilibrium of energy and matter. Observable matter is composed mostly of condensed photons (particles of electromagnetic field). In gravity field this equilibrium becomes shifted toward energy and matter evaporates into radiation.

And vice-versa, if we cool dense mixture of photons by adding of electromagnetic field or by fast removing them from gravitational field of giant black holes by pressure of radiation, we can achieve the separation and condensation of energy into particles of matter and antimatter. These particles condense above jets which are behaving like giant fountain and they collect matter at equatorial plane of black hole or star, thus forming flat galaxies and/or protoplanetary disks.

Mass-energy equilibrium is dynamic: if we compress matter in gravity field, it evaporates into radiation again in the similar way, like if we heat the carbon particles in atmosphere - as we can observe at the case of glowing stars. The speed of evaporation is energy density dependent, though: when we cool particles of matter fast by removing them from gravity field, we can stabilize it in the same way, like during fast cooling of carbon soot.

So we can understand Universe formation via common thermodynamics and illustrate it like common chemical processes in this way.
3 / 5 (4) Aug 18, 2009
The purpose of these vague models is explanatory (i.e. pedagogical) and it provides a feasible route, which enables to choose from increasing number of cosmological theories the most probable model and/or to reconcile them mutually.

We should realize, the proponents of particular theories aren't motivated very much in fast mutual reconciliation of their ideas (it keeps them significant and it keeps space for their private research) - so that unification of existing theories is the job waiting for layman society, not scientists as such. For example, if many people don't take Big Bang theory seriously by their intuition, even scientists can do nothing against it.
Aug 19, 2009
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not rated yet Aug 19, 2009
I wonder if researchers took into account asymmetric supernovae explosions in accreting white dwarfs or massive stars, as well as the effects of deflagration/detonation? An excellent article on these topics recently appeared in Science News: http://www.scienc..._secrets .

I still don't see why positron-electron generation couldn't originate from nearby pulsars or neutron stars, annihilating DM AND this newly theorized mode of their production, in varying amounts. All three might contribute to electron-positron fluxes detected in LEO, balloon borne experiments or by air shower arrays. According to Dr. Becker %u201CThis means that dark matter this means that it does not produce electrons and positrons in the same amount as giant stars and that one has to look for evidence of dark matter elsewhere%u201D. Why does this theory rule out any possibility of annihilating DM, especially in light of the poor statistics for electron/positron fluxes observed. Perhaps AMS will help to resolve this issue (the point was made for more sensitive observations in the paper). Perhaps DM is not due to annihilating particles at all, but from this article, it seems a stretch that all DM is non-annihilating. Btw, a 4-page preprint of this paper can be found here: .

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