Atomic corona surrounding GJ 436b simulated with the DSMC code. Only particles with coordinates − 10⁸ ≤ z ≤ 10⁸ m are shown. The black dot in the center shows the planet, the white area around the planet is the inner atmosphere modeled with a hydrodynamic code. The star is on the right. Blue dots are the neutral hydrogen atoms, which contribute to the Ly-α absorption. Red dots are the stellar wind protons, and green dots are the ionized hydrogen atoms of planetary origin. Radiation pressure is included.