The sun’s heliosphere protects the Earth from cosmic rays and dust from beyond the solar system. But it can get squeezed by very dense gas and dust, leaving us unprotected (Illustration: ESA)

THE sun provides ideal conditions for life to thrive, right? In fact, it periodically leaves Earth open to assaults from interstellar nasties in a way that most stars do not.

The sun protects us from cosmic rays and dust from beyond the solar system by enveloping us in the heliosphere – a bubble of solar wind that extends past Pluto. These cosmic rays would damage the ozone layer, …