2210473

Target RA (J2000): 54.183800 and deg Target Dec (J2000): 28.55046 and deg Gaia GMag: 12.19 Programme ID: CH_PR240024 PI of observing programme: Vach Title of programme: Confirmation of the first planet to be associated with the Pleiades cluster Abstract: The processes that drive planet formation and evolution within the first billion years are key in sculpting the planet population we observe today. Observing young planetary systems is the only opportunity to characterize these processes as they happen in real time. The Pleiades open cluster is one of the most well aged stellar groups at 120 Myr making it the ideal parent population to anchor planet evolution models. We propose to use CHEOPS to observe two transits of the first planetary candidate TOI-5358.01 kinematically affiliated with the Pleiades group. TOI-5358.01 is a mini-Neptune (P = 2.66 d Rp = 2.754 Rearth) orbiting the young K4V star TOI-5358 originally discovered by TESS. CHEOPS observations are critical in the confirmation and characterization of the system and will enable us to distinguish between different atmospheric characteristics such as clouds and haze in future transmission spectroscopy observations. [truncated! Please see actual data for full text]