  To date, the ability for observers to reveal the composition or thermal
structure of an exoplanet's atmosphere has rested on two techniques:
high-contrast direct imaging and time-series observations of transiting
exoplanets. The former is currently limited to characterizing young, massive
objects while the latter requires near 90 degree orbital inclinations, thus
limiting atmospheric studies to a small fraction of the total exoplanet
population. Here we present an observational and analysis technique for
studying the atmospheres of non-transiting exoplanets that relies on acquiring
simultaneous, broad-wavelength spectra and resolving planetary infrared
emission from the stellar spectrum. This method could provide an efficient
means to study exoplanet atmospheric dynamics using sparsely-sampled phase
curve observations or a mechanism to search for signs of life on non-transiting
exoplanets orbiting the nearest M-dwarf stars (such as Proxima Centauri). If
shown to be effective with James Webb Space Telescope (JWST) observations, the
method of measuring planetary infrared excess (PIE) would open up the large
population of nearby, non-transiting exoplanets for atmospheric
characterization.
