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Rocky Worlds DDT
Searching for atmospheres in rocky exoplanets orbiting small M-dwarfs
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earth
Program's main goal
The Rocky Worlds Director’s Discretionary Time (DDT) Program is a joint James Webb Space Telescope (JWST) and Hubble Space Telescope (HST) Program. It implements the top recommendations from the Working Group on Strategic Exoplanet Initiatives with HST and JWST, which compiled the views of the community in regards to many topics including specific concepts for a 500-hour DDT JWST exoplanet program [Redfield et al. (2024)ads] The program's main objectives are to search for evidence for atmospheres on rocky exoplanets orbiting M-dwarfs via secondary eclipse measurements at 15 um using the MIRI instrument, as well as to characterize the stellar UV properties with HST. Such a DDT follows the footsteps of other successful STScI-led community DDT past programs like
Hubble Deep Field
Williams et al. (1996) ads Williams et al. (2000) ads
Hubble Ultra Deep Field
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Hubble Frontier Fields
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ULLYSES
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Hubble Image

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HST Observations
The HST observations of the Rocky Worlds DDT are aimed to characterize the UV flux of the stellar hosts these exoplanets orbit. This is necessary to interpret why these objects have or don't have atmospheres. In particular, the UV flux can be used to estimate the Extreme Ultra Violet (EUV) radiation which defines the input energy these exoplanets receive today which can, in turn, help define the cumulative flux history on them that shapes -and the very existence of- their atmospheres. The HST/UV observations will also be used to monitor any flares the stars might give rise to, and which are also useful in understanding the current and past energy inputs in their atmospheres.
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JWST Observations
The JWST observations of the Rocky Worlds DDT will consist mainly of 15 μm time-series photometry using the MIRI instrument in order to observe secondary eclipse events (when the exoplanets pass behind their host stars.) This will enable the scientific community to study the depth of these secondary eclipses to study the dayside brightness of these rocky exoplanets. Large dayside fluxes and thus, deep eclipses, are expected to be produced when the exoplanets have poor energy redistribution, which is the expectation if the exoplanets don't have atmospheres. On the other hand, small dayside fluxes can be interpreted as planets efficiently redistributing energy, which could happen if they posses an atmosphere.

Planet Earth as seen from space by the ISS flying over Italy