Abstract.
This article presents a review on the observations and theoretical
modeling
of the evaporation of extrasolar planets. The observations and the
resulting constraints
on the upper atmosphere (thermosphere and exosphere) of the
.hot-Jupiters. are described.
The early observations of the first discovered transiting extrasolar
planet,
HD209458b, allowed the discovery that this planet has an extended
atmosphere of escaping
hydrogen. Subsequent observations showed the presence of oxygen and
carbon
at very high altitude. These observations give unique constraints on the
escape rate
and mechanism in the atmosphere of hot-Jupiters. The most recent
Lyman-alpha HST
observations of HD189733b and MgII observations of Wasp-12b allow for
the first
time a comparison of the evaporation from different planets in different
environments.
Models to quantify the escape rate from the measured occultation depths,
and an energy
diagram to describe the evaporation state of hot-Jupiters are presented.
Using this
diagram, it is shown that few already known planets like GJ876d or
CoRot-7b could
be remnants of formerly giant planets.
Keywords: Planetary systems - stars: individual (HD
189733, HD209458)