  In this paper, we estimate the X-ray emission from close-in exoplanets. We
show that the Solar/Stellar Wind Charge Exchange Mechanism (SWCX) which
produces soft X-ray emission is very effective for hot Jupiters. In this
mechanism, X-ray photons are emitted as a result of the charge exchange between
heavy ions in the solar wind and the atmospheric neutral particles. In the
Solar System, comets produce X-rays mostly through the SWCX mechanism, but it
has also been shown to operate in the heliosphere, in the terrestrial
magnetosheath, and on Mars, Venus and Moon. Since the number of emitted photons
is proportional to the solar wind mass flux, this mechanism is not very
effective for the Solar system giants. Here we present a simple estimate of the
X-ray emission intensity that can be produced by close-in extrasolar giant
planets due to charge exchange with the heavy ions of the stellar wind. Using
the example of HD~209458b, we show that this mechanism alone can be responsible
for an X-ray emission of $\approx 10^{22}$~erg~s$^{-1}$, which is $10^6$ times
stronger than the emission from the Jovian aurora. We discuss also the
possibility to observe the predicted soft X-ray flux of hot Jupiters and show
that despite high emission intensities they are unobservable with current
facilities.
