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HIGH-energy cosmic rays have more energy than they should. That makes sense if they are made from lumps of quarks called strangelets, say Danish scientists.

There is an upper limit to how much energy charged particles in space can have. Protons, for instance, cannot exceed 10¹⁹ electronvolts, yet some high-energy cosmic rays have been measured at 3 × 10²⁰ electronvolts, way above their theoretical limit.

That might mean they are made up of strangelets, says Jes Madsen from the University of Aarhus. While normal nuclei contain up and down quarks, strangelet nuclei also contain strange quarks, giving them a…