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Target RA (J2000): 3.955176 and deg Target Dec (J2000): 13.55619 and deg Gaia GMag: 11.39 Programme ID: CH_PR240007 PI of observing programme: Palethorpe Title of programme: CHEOPS can confirm an Earth-sized planet in the habitable zone of a metal-poor M-dwarf neighbour Abstract: The number of confirmed exoplanets has grown exponentially since the field was first established almost 30 years ago. However our understanding of how these planets form and evolve has been severely impacted by our ability to precisely characterise certain types of exoplanets. The characterisation of Earth-analogues in particular which are vital in gaining an understanding of our own planet’s history remains a very small pool. One such candidate first discovered by TESS is TOI-6251 b a nearby temperate Earth-sized planet orbiting a metal-poor M-dwarf. However multiples transits could have fallen in TESS’s data gaps – meaning that we are unable to conclusively state the period of the planet as either 12.7 or 25.5 days. Without this parameter the radius of the planet is unable to be precisely constrained meaning that even with our secured time to obtain high-precision RV observations from which the planets mass can be determined we would be unable to model the composition and interior structure. CHEOPS can confirm this habitable zone M dwarf planet however enabling us to further our knowledge on theories of how stellar compositional environment affects planetary internal structure as well as how planet formation and evolution has led to the observed density and radius valleys. With CHEOPS observations we can precisely pinpoint the orbital period and radius of TOI-6251 b – a planet of which the characterisation could unlock ground-breaking studies. [truncated! Please see actual data for full text]