IFL Science
By James Felton
June 11, 2025
In 1977, NASA launched the Voyager probes to study the Solar System’s edge, and the interstellar medium between the stars. One by one, they both hit the “wall of fire” at the boundaries of our home system, measuring temperatures of 30,000-50,000 kelvin (54,000-90,000 degrees Fahrenheit) on their passage through it.
There are a few ways you could define the edge of the Solar System – for instance, where the planets end, or at the Oort cloud, the boundary of the Sun’s gravitational influence where objects may still return closer to the Sun. One way is to define it as the edge of the Sun’s magnetic field, where it pushes up against the interstellar medium, known as the heliopause.