Free Astronomy Magazine November-December 2019

9 NOVEMBER-DECEMBER 2019 EXOPLANETS B elow, the in- stallation of Wide Field Cam- era 3 on the Hub- ble Space Tele- scope during Servicing Mission 4 in 2009. This is the instrument that, coupled with the STIS spectro- graph, allowed researchers to in- vestigate the at- mospheric compo- sition of K2-18 b. The graph on the right is the sum of all the photomet- ric measurements made by WFC3 during the eight transits analyzed by the Tsiaras and Benneke teams. [NASA, B. Ben- neke et al.] weight: 1) we have known for several years of large planets that show the presence of water vapor in their atmospheres, but these worlds are certainly in- hospitable given, at the very least, their very high tempera- tures; 2) water is the second most common molecule in the uni- verse after molecular hydrogen (H 2 ) and has even been recognized in the spectrum of the Sun, so it should not be surprising to find it in the atmosphere of a medium-sized planet orbiting inside the hab- itable zone of a star. Given the above, the clamor around the dis- covery of water vapor in the atmosphere of super-Earth K2-18 b last September appears Before assessing the extent of the new dis- covery, we have to stress a few points that will help us give the discovery the right