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Verbal·Information and Ideas·Central Ideas and Details
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When a planet crosses in front of a star, astronomers usually interpret the resulting dip in brightness as evidence about the planet’s size. Dark starspots can complicate that interpretation: if a planet crosses an unusually bright, unspotted portion of a heavily spotted star, the dip can appear deeper than it otherwise would. Astronomers therefore model the star’s changing surface brightness before estimating the planet’s radius.
Which choice best states the main idea of the text?
A
Starspots can distort transit measurements, so astronomers account for stellar brightness variation when estimating a planet’s size.
B
A planet’s radius determines how many starspots form on its host star.
C
Astronomers can estimate a planet’s size only when its host star has no spots.
D
A planet appears smaller whenever it crosses an unspotted part of a star.