  Both young stars and multi-planet systems are primary objects that allow us
to study, understand and constrain planetary formation and evolution theories.
We validate the physical nature of two Neptune-type planets transiting TOI-942
(TYC 5909-319-1), a previously unacknowledged young star (50+30-20 Myr)
observed by the TESS space mission in Sector 5. Thanks to a comprehensive
stellar characterization, TESS light curve modelling and precise
radial-velocity measurements, we validated the planetary nature of the TESS
candidate and detect an additional transiting planet in the system on a larger
orbit. From photometric and spectroscopic observations we performed an
exhaustive stellar characterization and derived the main stellar parameters.
TOI-942 is a relatively active K2.5V star (logR'hk = -4.17+-0.01) with rotation
period Prot = 3.39+-0.01 days, a projected rotation velocity vsini=13.8+-0.5
km/s and a radius of ~0.9 Rsun. We found that the inner planet, TOI-942b, has
an orbital period Pb=4.3263+-0.0011 days, a radius Rb=4.242-0.313+0.376 Rearth
and a mass upper limit of 16 Mearth at 1-sigma confidence level. The outer
planet, TOI-942c, has an orbital period Pc=10.1605-0.0053+0.0056 days, a radius
Rc=4.793-0.351+0.410 Rearth and a mass upper limit of 37 Mearth at 1-sigma
confidence level.
