I know spectroscopy of light in visible wavelengths is very effective for studying and determining the chemical composition of bodies within the solar system and bright objects outside of it. However, can this same method be used with exoplanets?

In looking about some related articles, I've learned that it is possible, if a planet passes between us and its star, to filter out the star's light leaving only what passes through the planet's atmosphere.
But what if there is no such occultation? Can we filter out the star's light in other wavelengths like UV or infrared and look at just the planet via its own emitted radiation (assuming the planet is large and hot as these are what we are most able to detect at this time)?

  • $\begingroup$ I think James Webb (JWST) is expected to do that. Current telescopes, I think the answer is no or not well. jwst.nasa.gov/origins.html $\endgroup$
    – userLTK
    Feb 29, 2016 at 3:37

1 Answer 1


This can be done by high-contrast imaging.

Currently it is only feasible for a very limited class of systems (e.g. HR 8799) since it is difficult to achieve the required angular resolution (0.1 arcsecs for exoplanets at a distance 10 parsec) with today's adaptive optics.

Future large telescopes such as the European Extremely Large Telescope are designed for direct imaging as well as visible and near-infrared spectroscopy of exoplanets.

  • 1
    $\begingroup$ You may wish to clarify that "high contrast imaging" yields limited spectroscopic information in the infrared part of the spectrum. Adaptive optics does not work at visible wavelengths. $\endgroup$
    – ProfRob
    Feb 29, 2016 at 22:48

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