Yesterday the K2 mission detected transit events of objects passing in front of a number of M dwarfs which could turn out to be rocky planets. If some of these planets host atmospheres, could the JWST detect IR absorption lines from molecules in these atmospheres?

What would be the expected limiting distance for these stars to allow for such measurements by the JWST?

  • $\begingroup$ Table 1 here might interest you, but it's not an answer to your question. $\endgroup$
    – HDE 226868
    Jul 19, 2016 at 21:59
  • $\begingroup$ Related: astronomy.stackexchange.com/questions/11186/… $\endgroup$
    – called2voyage
    Jul 21, 2016 at 13:36
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    $\begingroup$ @dualredlaugh I'm assuming you mean detecting spectral lines from planetary atmospheres of rocky planets in the habitable zone. Hot Jupiters and Neptunes are already being studied, however the rocky planets you are talking about will have to be close for JWST (not sure how close/ depends on several characteristics). Hopefully TESS will find a few. If we do find close enough planets, we may not have to wait for JWST. Check this out! nasa.gov/press-release/… $\endgroup$ Jul 27, 2016 at 4:57
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    $\begingroup$ note: One of my favorites is Kepler2-3d, however at 137 light years it may be just outside JWST's range to look for biosignatures.K2-18b is interesting at 111 light years and may be a very large waterworld, but more likely is a "mini-Neptune" at 2.24 Earth radius. Once we have a telescope that can get biosignatures of transiting planets 200 light years away, I want to find a highly "insulated" moon orbiting Kepler-16b (image the view from that one!) $\endgroup$ Jul 27, 2016 at 5:13
  • $\begingroup$ It's hard to answer anything but yes, since it is always possible that they have some sort of detectable atmosphere. I.e. You need to define the atmosphere before one can say whether it will be detectable. $\endgroup$
    – ProfRob
    Jul 2, 2017 at 8:28

1 Answer 1


According to this article, the TRAPPIST-1 system is supposed to be studied by JWST with the potential to detect atmospheres' composition in infrared band. So at last 40 ly (approx. 12 pc) should work. Somewhere else I read there is an assumption to study earth-like exoplanetary atmospheres at distance of 10-20 pc. But it might be better to see it from different angle: the real limit is due to the produced light energy/intensity, not the distance itself. For example, see an article on exoplanet transit spectroscopy.


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