True or false: a 10 M⊙ star is 10 times more luminous than a 1 M⊙ star.

Two main-sequence stars have the same spectral class; Star 1 is 100× dimmer. By what factor is Star 1 more distant? (Recall that F ∝ 1/r²)

Two stars have the same spectral class; Star 1 is 100× dimmer than Star 2. What can you conclude about their distances?

Predict first. For a 1.5 M⊙ main-sequence star, is the lifetime longer or shorter than the Sun’s? Choose your prediction before calculating.

Calculate. Using t/t⊙ = (M/M⊙)^−2.5 and t⊙ = 10 Gyr, lifetime (Gyr) of a 1.5 M⊙ star?

On the main sequence, L/L⊙ = (M/M⊙)^3.5. What is L/L⊙ for M = 1.5 M⊙?

Predict first. Antares has L = 9120 L⊙ and T = 3340 K. Before calculating R/R⊙: will its radius be larger or smaller than the Sun?

Look up Antares on SIMBAD

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Calculate. Antares has L = 9120 L⊙ and T = 3340 K. Taking T⊙ = 5770 K, what is R/R⊙?

On a standard Hertzsprung–Russell (H–R) diagram, which statement is correct?