Re:An Ultrahot Exoplanet Has Metallic Skies
by cgriswald on Sunday August 19, 2018 @12:12PM
(#17794821)
It works basically like that. The spectrum of the star will be an absorption spectrum. The star produces a continuous spectrum and then the atoms in its atmosphere absorb specific wavelengths. The light then travels through the planet's atmosphere where other atoms and molecules absorb other wavelengths; the signatures of which are known, telling scientists the makeup of the atmosphere.
You are totally right, the best response is a clear, calm explanation. Unfortunately, the time, energy, and expertise to do so is not always available. It's in moments like those where I hesitate between ignoring the comment entirely and downvoting.
As for transit spectroscopy, I'm going off memory/rederivation/speculation here (not sure how much of each), but I believe it works by first taking the spectrum of the parent star by itself, then observing the spectrum of the starlight travelling through the transiting planet's atmosphere, and then diffing the two results to isolate the spectrum of the planet's atmosphere.