Ultra High Energy Cosmic Rays (uhecr)

Extremely energetic subatomic particles (mostly protons, but also some heavier atomic nuclei) with energies >109 MeV. The record holder so far is a UHECR with an energy of 6 × 1014 MeV! UHECRs are observed only in cosmic ray showers, because of their extremely low numbers. The source of UHECRs is a mystery, as is the mechanism that accelerates particles to these energies. They have sufficient energy to escape the typical magnetic field of a spiral galaxyGalaxy with spiral arms. These are classified based on their appearance in optical light, into those in which the arms radiated from a central bulge (classic spirals, S), and those where the arms radiated from a central bar (barred spirals, SB). Both types of spiral galaxies have a central bulge, and most UHECRs are probably of extragalactic origin. Possible sources include active galactic nuclei, dormant quasars with associated supermassive black holes and galaxyConcentration of 10⁶ to 10¹² stars, dust and gas, that are gravitationally bound. Our galaxy contains ~2 × 10¹¹ stars. There are four main types of galaxies: • Elliptical
• Lenticular
• Spiral
• Irregular
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