Closest orbital distance at which an Earth-like planet orbiting the stars in our sample would be able to sustain the present-day (red circles) and the young (3.4 Gyr ago, grey squares) Earth’s magnetospheric size, assuming it has the same magnetic field as the Earth. We use a sample of 15 active stars for which large-scale surface magnetic-field maps were reconstructed, to determine the magnetic pressure at the planet orbit and hence the largest extent of its magnetosphere. Planets orbiting at a closer orbital radius would experience a stronger stellar magnetic pressure, which could reduce the size of the planet’s magnetosphere significantly, exposing the planet’s atmosphere to erosion by the stellar wind. For reference, we show the inner/outer edge of the HZ for 1-Gyr-old low-mass stars (solid lines).