How Do Astronomers Know That Pulsating Variable Stars Are Actually

question 24

Multiple Choice

How do astronomers know that pulsating variable stars are actually expanding and contracting in diameter?

• A) it is clear just by looking at the light curve
• B) they discover this by looking at an H-R diagram
• C) they can measure a regularly varying Doppler shift in the spectral lines
• D) they can measure the star's changing pull on a companion star around it
• E) astronomers are just guessing; at the distances of the stars, there is no way to show that stars are expanding and contracting

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Earnings that exceed the minimum acceptable return on an investment or project, often used in performance measurement and compensation.

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