Question

The colour of a star is an indication of its

• A. Size
• B. Density
• C. Temperature
• D. Distance from earth

Answer 1

Answer:

C. Temperature

Stellar Classification based on Temperature

• Temperature Correlation: The color of a star is a direct manifestation of its surface temperature. This relationship is governed by Wien's Displacement Law, which states that the peak wavelength of light emitted by a blackbody is inversely proportional to its temperature.
• Color Spectrum: Stars are categorized by their spectral classes (O, B, A, F, G, K, M).
  • Blue stars (Class O and B): These are the hottest, with surface temperatures exceeding 30,000 Kelvin.
  • Yellow stars (Class G): These have moderate temperatures, similar to the Sun, which is approximately 5,778 Kelvin.
  • Red stars (Class M): These are the coolest, with temperatures typically below 3,500 Kelvin.
• Blackbody Radiation: Astronomers treat stars as approximate blackbodies. As a star's temperature increases, the peak of its emitted light spectrum shifts toward shorter, bluer wavelengths. Conversely, cooler stars emit more energy at longer, redder wavelengths.
• Evolutionary Context: While temperature determines color, this temperature is influenced by the star's mass, chemical composition, and evolutionary stage (e.g., Main Sequence, Red Giant, or White Dwarf).
• Hertzsprung-Russell Diagram: This essential tool for stellar evolution plots stars based on their luminosity versus their surface temperature (color), allowing scientists to classify stars into different life stages.