News from the Frontiers of Cosmology: A companion to the book The Edge of Physics
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New supernova might undermine dark matter search


THE DISCOVERY OF A NEW TYPE OF supernova, reported in this week’s Nature, could have implications for indirect detection of dark matter.

This supernova, SN2005E, spewed out calcium and titanium. The calcium, of course, is the stuff of our bones, showing even more emphatically — not that there was ever any doubt — that we are  all “made of star stuff”, as Carl Sagan poetically put it.

The titanium is far more interesting. It’s radioactive, and emits positrons as it decays. Over the past couple of years, balloon and satellite-based experiments, such as ATIC and PAMELA, have reported seeing an excess of positrons coming from outer space. This excess has been attributed to the anniliation of dark matter particles, though, theorists have struggled to reconcile the various results. The only serious contender for a source of positrons are pulsars, and we don’t know enough about the distribution of pulsars to rule them out or in.

Now, astronomers are saying that this new class of supernova could be quite common, and if the titanium ejected from them is putting out positrons, it could account for the excess being seen by experiments.

Where does that leave the claims of dark matter detection? In a spot of bother. Of course, this doesn’t mean that dark matter doesn’t exist, but it does pose uncomfortable questions about the claims of the past years.

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