In astronomy, what's the term for the region of space where the sun's solar wind has a significant influence?
And the answer: heliosphere.
The sun sends out a constant flow of charged particles called the solar wind, which travels far beyond the planets, before being slowed down by gas and dust at the far reaches of our solar system. This forms a giant bubble around the sun and its planets, known as the heliosphere.
The heliosphere is responsible for electrically neutral gas, ionized gas, and interstellar dust that form our solar system’s local galactic environment. Although its exact limits remain unknown, it's thought to reach out some 9 or 10 billion miles – far beyond Pluto, at the edge of our solar system.
The heliosphere interacts quite differently with planets, primarily depending upon whether or not that planet has an internally generated magnetic field. Those that do – Earth, Mercury, and the outer planets – tend to have atmospheres which are protected from direct exposure to the solar wind by the terrestrial magnetic field. Those that don't – Mars and Venus, plus our Moon – suffer atmospheric erosion by the solar wind, and greatly impact the climate of the planet.
Thanks to the bubble of the heliosphere, we are somewhat protected from any rogue, charged particles that could potentially enter our solar system and disrupt life as we know it. Now everyone say, "Thank you, Sun!"
Learn more about the heliosphere below.