How can astronomers measure the composition of an extrasolar planet's atmosphere?
A)by measuring the composition of the host star; the planet must have formed from the same initial material
B)by comparing spectra for when the planet is in transit or eclipse with spectra taken at other times
C)by measuring how brightly the planet glows in infrared light
D)by measuring the Doppler shift of the host star

Question

Quizplus · Accepted Answer

By comparing spectra for when the planet is in transit or eclipse with spectra taken at other times, astronomers can look for the chemical signatures of the planet's atmosphere. The planet blocks some of the starlight during transit, allowing astronomers to see the light that passes through the planet's atmosphere. By comparing this spectrum to the spectrum of the star alone, astronomers can detect the chemical composition of the planet's atmosphere.

How Can Astronomers Measure the Composition of an Extrasolar Planet's