In The Observatory @Donald.McLean linked to Scientists will peer at first galaxies with James Webb telescope which says in part:

The new telescope will augment science performed by Hubble, not necessarily replace it, (Nestor) Espinoza said. He is part of the James Webb team at the organization that manages science done with such space instruments, a Baltimore-based a non-profit consortium of scientists that advises NASA.

Espinoza will serve as the principal scientist on projects in which the Webb telescope will examine two planets in distant planetary systems. One of them, K2-141b, is about 50 percent larger than Earth, while the other, WASP-63b, is a gas giant similar to Jupiter.

"Hubble can't perform the kinds of observations we need to learn about the atmospheres of these planets, or other details, since it was designed before the first planets outside our solar system were detected," Espinoza said.


Many of the proposed tasks for the Webb telescope were planned and approved in the 1990s as the observatory was under initial development, said Klaus Pontoppidan, an astronomer and Webb project scientist at the institute.

"We've just added the final projects that will be included during the first year or 13 months," Pontoppidan said.

I don't know if K2-141b and WASP-63b are the first exoplanets that JWST will look at in the first round of observations, or just two examples of many. I also don't know if these exoplanets had even been discovered yet when "(m)any of the proposed tasks for the Webb telescope were planned and approved in the 1990s..."

So I'd like to ask:

Question: Were K2-141b (50 percent larger than Earth) and WASP-63b (gas giant similar to Jupiter) selected as the first two exoplanet atmospheres for JWST to look at during its first year of observations? If so, why? If not, how many other exoplanet atmospheres are planned to be studied during this period?


1 Answer 1


The list of JWST approved programs for Cycle 1 (12 months long, starting after the 6 month long commissioning phase following launch) is available here. If you unfold the Exoplanets and Disks science category, you will see the programs, along with the links to proposal abstracts and target lists.

Looking at the proposal titles only, the exoplanet targets for atmospheric studies include:

The Espinoza et al. proposal is proposal number 2159 is one of two to study K2-141b. So K2-141b and WASP-63b are just two of the exoplanets that will be studied by JWST in the first cycle, with others likely in following cycles.

In the overall summary of the JWST Cycle 1 proposal process that was made available to the community, exoplanets accounted for 928 out of the 3500 hours allocated to small programs (slide 7). The exoplanets to be studied are chosen by the individual investigation teams that submit the proposals based on what particular aspects of the atmosphere they are trying to study. These proposals are evaluated by the various exoplanet subpanels of the time allocation committees and by Space Telescope Science Institute (STScI; who operate JWST and HST) staff for scientific merit, technical feasibility, capabilities of the proposing team and optimal use of JWST, a process which is common to almost all competed observing facilities. (The science panels are supposed to only consider the scientific merit, the technical feasibility is handled by STScI staff; this process has been improved by STScI for recent HST and all JWST Cycles by employing Dual Anonymous Peer Review where the panel doesn't know the identity of the proposers and the proposers don't know the membership of the review panels)

  • $\begingroup$ Thank you for your (as always) thorough answer! $\endgroup$
    – uhoh
    May 19, 2021 at 22:42

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