A Cepheid star is a type of variable star, which means its brightness is not constant. The relationship between the brightness of a
Cepheid star and its period, or length of its pulse, is given by M = -2.78(log P) - 1.35, where M is the absolute magnitude, or
brightness of the star, and Pis the number of days required for the star to complete one cycle. What is the absolute magnitude of
a star that has a period of 45 days? Use a calculator. Round your answer to the nearest hundredth.
-5.95
-4.60
3.25
4.60

magnitude, in astronomy, measures the brightness of a star or other celestial body. The brighter the object, the lower the number assigned as a magnitude. In ancient times, stars were ranked into six magnitude classes, the first magnitude class containing the brightest stars.

How do you find the magnitude of a star?

Mv = m - 2.5 log[ (d/10)2 ]. Stars farther than 10 pc have Mv more negative than m, that is why there is a minus sign in the formula. If you use this formula, make sure you put the star's distance d in parsecs (1 pc = 3.26 ly = 206265 AU).

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The absolute magnitude of a 45-day star is -5.95.

How big is the star?

The magnitude measures the brightness of a star or other celestial body in astronomy. The brighter the object, the lower the number assigned as a magnitude. In ancient times, stars were divided into six magnitudes, the first of which contained the brightest stars.

How do you find the size of a star?

Mv = m-2.5log [(d / 10) 2]. Stars over 10 pc have a minus sign in the formula because Mv is more negative than m. When using this formula, enter the star distance d in parsecs (1 pc = 3.26 Ly = 206265 AU).

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