The Mission Concept for OWL Which Will Detect
Cosmic Rays at the Highest Energies

The Mission Concept for OWL Which
Will Detect Cosmic Rays at the Highest Energies

Mystery of the Highest Energy Cosmic Rays?

EXTRAORDINARY ENERGY, RARITY: The highest energy of a detected cosmic ray is 3x1020 eV (electron volts), equivalent to about 12 calories, more than ten-million times greater than the maximum energy achievable with the largest planned particle accelerators on Earth. This recently detected event was concentrated in a single "elementary" particle, the highest energy such fundamental chunk of matter yet to be found in nature. Only seven other events with energy above about 1020 eV have been observed.

LIKELY EXTRAGALACTIC ORIGIN: There is no known mechanism in our Galaxy which can accelerate particles to the observed energies. Additionally, the magnetic field of our galaxy is too weak to contain the highest energy cosmic rays, if they are charged particles.

UNKNOWN SOURCES: If they are extragalactic, the highest energy cosmic rays will interact with the pervasive three-degree thermal cosmic microwave background radiation, which degrades their energy. As a result the observed cosmic rays cannot originate from distances greater than a few percent of the distance to the horizon of the universe. There are no plausible sources this close to our galaxy.

NEW PHYSICS? Possibly the highest energy cosmic rays have an exotic, "top down" source. The annihilation of topological defects, e.g. "strings", remaining from phase transitions in the early Universe, would produce charged particles with energies extending well above the highest energy cosmic rays.

AN EXPERIMENT: High energy cosmic rays may be observed when they interact with the earth's atmosphere, producing a cascade of millions of secondary particles which move through the atmosphere at the speed of light and produce fluorescence. The fluorescent light from these cascades may be observed from space, and the energy and arrival direction of the cosmic rays determined.

Mission: OWL


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