The vast bubble-like region of space dominated by the solar wind and the Sun's magnetic field, extending far beyond the orbit of Pluto. It acts as a partial shield protecting the solar system from interstellar radiation and cosmic rays.
From Greek 'helios' meaning 'sun' and Latin 'sphaera' meaning 'sphere.' The term was introduced in the 1960s as scientists began to understand that the Sun's influence extends far beyond the visible planets, creating a distinct region in space.
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