The Webb telescope will study two strange rocky alien worlds

Two extravagant rocky alien worlds will end up in the crosshairs of the new James Webb space telescope in the first year of its scientific mission, which is expected to start in a few weeks. With his high-precision spectrographs, Webb will study in detail the lava-covered planet ’55 Cancri e ‘and the airless planet’ LHS 3844 b ‘. This was announced by the members of the mission’s scientific consortium, led by the space agencies of the United States (NASA), Europe (ESA) and Canada (CSA).

The two planets outside the Solar System (exoplanets) are classified as ‘super-Earths’, due to their size and rocky composition.

55 Cancri is orbiting less than 2.4 million kilometers from its star (one twenty-fifth of the distance between Mercury and the Sun), completing an orbit in less than 18 hours. With surface temperatures well above the melting point of typical rock minerals, it is possible that the illuminated side of the planet is covered in oceans of lava. Planets so close to their star usually always face the same face, but previous observations made with the Spitzer telescope indicate that the hottest region of 55 Cancri e is not the one most directly exposed to the star and the heat detected in the illuminated part varies. The Webb telescope with its NIRCam will try to solve this enigma, trying to understand if the phenomenon is due to the presence of a dynamic atmosphere that causes heat to move around the planet or if the planet rotates on itself with a day-night cycle. .

LHS 3844 also orbits very close to its star, completing one revolution in 11 hours. However, because the star is relatively small and cold, the planet is not hot enough to melt the surface. Furthermore, Spitzer’s observations indicate that the planet is very unlikely to have a consistent atmosphere: for this reason it represents a unique opportunity to study with the MIRI instrument the thermal emission of the exoplanet’s surface in order to determine its composition.


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