Views of HD 97658 b theoretical exosphere from the perpendicular to the orbital plane. Neutral hydrogen particles are colored as a function of their Doppler radial velocity according to the scale on the right axis. The planet is the small disk on the planetary orbit (green line). The dashed black lines limit the LOS toward Earth (the star is toward the top of the figure). Although the transit observations in the Lyman-α line are consistent with the absence of atmospheric escape, they still allow for the formation of a compact (upper panel, R_trans = 3 R_pl, Ṁ_H⁰ = 2 × 10⁷ g s^-1, v_trans = 1 km s^-1, T_iso = 1000 K) or low-density exosphere (lower panel, R_trans = 6 R_pl, Ṁ_H⁰ = 3 × 10⁶ g s^-1, v_trans = 10 km s^-1, T_iso = 8000 K). We note the comet-like shape of the exosphere, blown away by the strong radiation pressure, and its length that arises from the low photoionization rate.