Student Article
Does Our Solar System Have a Protective Wall?
Solar wind (noun): A stream of particles from the Sun.
Interstellar medium (noun): The matter and radiation that exist in the space between star systems.
Cosmic rays (noun): Energetic particles from space.
Plasma (noun): A state of matter similar to gas but consisting of charged particles.
Astronomical unit (noun): The average distance between the Earth and the Sun.
Curious about the boundary of our Solar System? Let's delve into the concept of the heliopause!
Meet the edge: the heliopause
The boundary of our Solar System is marked by the heliopause, where the solar wind from the Sun meets the interstellar medium (ISM). The solar wind is a constant stream of particles, including protons, electrons, and alpha particles, emitted by the Sun. The heliopause represents the edge of the heliosphere, the bubble of space dominated by the Sun's magnetic field and particle emissions.
How far out is it?
The heliopause is located approximately 120 astronomical units (AU) from the Sun in the direction facing the interstellar wind and extends to at least 350 AU in the opposite direction. One AU is the average distance between the Earth and the Sun.
Space force field: why it matters
This boundary is significant because it deflects about 70% of energetic cosmic rays, providing crucial protection for Earth and humans from harmful interstellar radiation. NASA's Voyager 1 and Voyager 2 spacecraft, launched in 1977, crossed the heliopause on August 25, 2012, and November 5, 2018, respectively. Instruments onboard Voyager 2 discovered that as plasma at the heliopause slows down, it becomes denser, and the local magnetic field increases.
Hot but harmless
Just beyond the heliopause, the temperature of the ISM is astonishingly high, ranging from 53,492-90,032°F (29,700-50,000°C). This region has been sensationally dubbed the "wall of fire." However, this term is misleading because, despite the high temperature, the plasma is extremely diffuse, allowing spacecraft like the Voyager probes to pass through the heliopause unharmed.
© Dr. Alastair Gunn / Our Media
Solar wind (noun): A stream of particles from the Sun.
Interstellar medium (noun): The matter and radiation that exist in the space between star systems.
Cosmic rays (noun): Energetic particles from space.
Plasma (noun): A state of matter similar to gas but consisting of charged particles.
Astronomical unit (noun): The average distance between the Earth and the Sun.