A system for categorizing stars based on their surface temperature and spectral characteristics, primarily using the OBAFGKM sequence. Each class represents different stellar properties, with O-type being the hottest and bluest, and M-type being the coolest and reddest.
Developed in the early 20th century at Harvard Observatory, initially by Annie Jump Cannon who refined earlier alphabetical systems. The current OBAFGKM sequence represents a temperature-based ordering that replaced the original alphabetical classification.
The stellar classification system is like a cosmic fingerprinting database! Each star's spectrum tells us not just its temperature, but also its mass, age, and ultimate fate. The famous mnemonic 'Oh Be A Fine Girl/Guy, Kiss Me' has helped generations of astronomers remember this stellar hierarchy that spans from blue giants destined for explosive deaths to red dwarfs that will outlive our universe's current age.
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