Suppose a Cepheid variable has been identified, and its period of brightness variability is measured to be 30 days. Its apparent magnitude is +23.3. How far away is it? (See Figure 19-21 of Universe, 11th ed.) Note: The Sun's apparent magnitude is -26.7.

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The Answer of Suppose a Cepheid variable has been identified, and its period of brightness variability is measured to be 30 days. Its apparent magnitude is +23.3. How far away is it? (See Figure 19-21 of Universe, 11th ed.) Note: The Sun's apparent magnitude is -26.7. A)3.1 × 10⁴ pc B)4.8 × 10⁶ pc C)6.0 × 10⁷ pc D)8.7 × 10⁹ pc

Suppose a Cepheid Variable Has Been Identified, and Its Period