  As a rule, the orbital velocities of "hot Jupiters," i.e., exoplanets with
masses comparable to the mass of Jupiter and orbital semi-major axes less than
0.1 AU, are supersonic relative to the stellar wind, resulting in the formation
of a bow shock. Gas-dynamical modeling shows that the gaseous envelopes around
"hot Jupiters" can belong to two classes, depending on the position of the
collision point. if the collision point is inside the Roche lobe of the planet,
the envelopes have the almost spherical shapes of classical atmospheres,
slightly distorted by the influence of the star and interactions with the
stellar-wind gas; if the collision point is located outside the Roche lobe,
outflows from the vicinity of the Lagrangian points $\mathrm L_1$ and $\mathrm
L_2$ arise, and the envelope becomes substantially asymmetrical. The latter
class of objects can also be divided into two types. If the dynamical pressure
of the stellar-wind gas is high enough to stop the most powerful outflow from
the vicinity of the inner Lagrangian point $\mathrm L_1$, a closed
quasi-spherical envelope with a complex shape forms in the system. If the wind
is unable to stop the outflow from $\mathrm L_1$, an open aspherical envelope
forms. The possible existence of atmospheres of these three types is confirmed
by 3D numerical modeling. Using the typical "hot Jupiter" HD 209458b as an
example, it is shown that all three types of atmospheres could exist within the
range of estimated parameters of this planet. Since different types of
envelopes have different observational manifestations, determining the type of
envelope in HD 209458b could apply additional constrains on the parameters of
this exoplanet.
