The magazine of the european research area European Commission Copenhagen, a missed chance?

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A black day 

for dark matter 

A few years back astrophysicists 

were pondering over the origin 

of the flow of electrons and 

positrons detected in the Milky 

Way. The most likely hypothesis 

at the time was that these ele-

mentary particles were produced 

by the mysterious ‘dark matter’. 

In fact dark matter has nothing to 

do with this, according to a study 

published in August 2009 in 

Physical Science Letters by a team 

including astrophysicist Julia 

Becker from the Ruhr-Universität 

Bochum and physicist Wolfgang 

Rohde from the Technische 

Universität Dortmund in Germany.

According to this study, the flows 

that have been detected in fact 

come from the plasma ejected 

during the explosion of huge stars 

having a mass of more than 

15 times that of the sun. This 

accelerated plasma collides with 

the solar wind consisting of 

particles from earlier explosions to 

form a shock wave. Depending on 

the alignment of this shock wave 

with the magnetic field of the 

remnant star, the emerging signal 

is sometimes weak, sometimes 

very high energy. This model fits 

© Shutt

erst

ock/L

ulu Duraud

© Shutt

erst

ock/S

ebastian K

aulitzk

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“And all of a sudden the memory 

became visible to me. This taste was that 

of the little piece of madeleine cake.”  

Marcel Proust

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