The TRAPPIST-1 exoplanetary system is made up of seven rocky planets, all about the same size as Earth, orbiting a very cool and faint star. Three of these planets are located in the “habitable zone,” where conditions might allow liquid water to exist. These planets are some of the best-studied worlds beyond our solar system, and they’re also the most promising for exploring temperate rocky planets using the James Webb Space Telescope (JWST). In particular, the two closest planets to the star, TRAPPIST-1 b and c, get enough heat from their star for us to measure their temperatures by looking at their thermal emission in the infrared. This is done during a “secondary eclipse,” when the planet passes behind the star from our viewpoint. In this presentation, I’ll start by explaining what we know so far about the TRAPPIST-1 system. Then, I’ll share the latest findings from JWST’s observations of these two planets, including recently published data. Finally, I’ll show how these observations help us figure out if these planets have atmospheres—or, if not, what their surfaces might be made of.
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