The Sun warms the Earth, making it habitable for people and animals. But that’s not all it does, and it affects a much larger area of space. The heliosphere, the area of space influenced by the Sun, is over a hundred times larger than the distance from the Sun to the Earth.
The Sun is a star that constantly emits a steady stream of plasma – highly energized ionized gas – called the solar wind. In addition to the constant solar wind, the Sun also occasionally releases eruptions of plasma called coronal mass ejections, which can contribute to the aurora, and bursts of light and energy, called flares.
The plasma coming off the Sun expands through space, along with the Sun’s magnetic field. Together they form the heliosphere within the surrounding local interstellar medium – the plasma, neutral particles and dust that fill the space between stars and their respective astrospheres. Heliophysicists like me want to understand the heliosphere and how it interacts with the interstellar medium.
The eight known planets in the solar system, the asteroid belt between Mars and Jupiter, and the Kuiper Belt – the band of celestial objects beyond Neptune that includes the planetoid Pluto – all reside within the heliosphere. The heliosphere is so large that objects in the Kuiper Belt orbit closer to the Sun than to the closest boundary of the heliosphere.
