  We show that the exoplanet-host star iota Horologii, alias HD17051, which
belongs to the so-called Hyades stream, was formed within the primordial Hyades
stellar cluster and has evaporated towards its present location, 40 pc away.
This result has been obtained unambiguously by studying the acoustic
oscillations of this star, using the HARPS spectrometer in La Silla Observatory
(ESO, Chili). Besides the fact that $\iota$ Hor belongs to the Hyades stream,
we give evidence that it has the same metallicity, helium abundance, and age as
the other stars of the Hyades cluster. They were formed together, at the same
time, in the same primordial cloud. This result has strong implications for
theories of stellar formation. It also indicates that the observed
overmetallicity of this exoplanet-host star, about twice that of the Sun, is
original and not caused by planet accretion during the formation of the
planetary system.
