Heliosphere

The vast region of space shaped by the Sun’s solar wind and magnetic field, extending outward until they meet the surrounding interstellar medium.

Solar wind: A continuous flow of charged particles released from the Sun’s outer atmosphere. Its outward pressure and magnetic field create and shape the heliosphere.
Voyager 1: A NASA spacecraft launched in 1977 that crossed the heliopause in 2012. Its plasma and particle measurements established that it had entered interstellar space.
Sun: The star at the center of the Solar System, powered by nuclear fusion in its core. Its atmosphere supplies the particles and magnetic field that fill the heliosphere.
Astrosphere: A cavity in interstellar space shaped by the wind and magnetic field of a star. The heliosphere is the astrosphere produced by the Sun.
Termination shock: A boundary where the supersonic solar wind slows abruptly to subsonic speed. The solar wind crosses this shock before entering the heliosheath.
Voyager 2: A NASA spacecraft launched in 1977 that crossed the heliopause in 2018. Its crossing supplied a second, differently located sample of the boundary.
Solar corona: The Sun’s hot, tenuous outer atmosphere, visible as a halo during a total solar eclipse. The solar wind flows outward from the corona.
Stellar wind: A flow of charged particles emitted by a star’s atmosphere. The solar wind is the Sun’s instance of this broader stellar process.
Heliosheath: The turbulent outer layer of solar wind between the termination shock and heliopause. This region holds slowed solar wind just inside the heliosphere’s outer boundary.
Voyager program: A pair of NASA probes launched in 1977 to explore the outer planets and interstellar space. Both spacecraft extended planetary exploration into the heliosphere’s outer regions.

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