Why are some stars red and others blue?
Show answer & explanation
Answer: Temperature affects color
Different chemical compositions — Wrong. Composition affects spectra details, but color primarily indicates temperature—blue stars are hottest, red stars coolest.
Age determines star color — Wrong. Stars evolve and change temperature/color over lifetimes, but at any moment, color indicates current temperature, not age directly.
Temperature affects color ✓ — Correct! Star color directly reveals surface temperature—blackbody radiation. Blue/blue-white stars are hottest (>30,000K)—Rigel, Spica. White/yellow stars are medium (5,000-10,000K)—Sun (~5,800K), Sirius. Red stars are coolest (2,000-3,500K)—Betelgeuse, Antares. Wien's Law: peak wavelength shifts bluer as temperature increases. O-B-A-F-G-K-M spectral classification ranks from hot to cool. Temperature = color!
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