Nasa found a ‘wall of fire’ at the edge of our solar system

In 1977, Nasa launched the Voyager twin probes to study the very edge of our solar system. As they made their journeys, they both hit a 'wall of fire' where temperatures reached 30,000-50,000 kelvin (54,000-90,000 degrees Fahrenheit) and experts were unsure if they could ever pass through it to discover what lies beyond (Picture: Getty)

This wall sits at the heliosphere – the point where the Sun’s influence fades. But according to Nasa’s Heliophysics program, the heliosphere, which is a protective bubble created by the Sun’s solar wind, goes past Pluto and serves as the boundary separating solar winds from interstellar winds. It is not a hard wall or an edge but a zone (Picture: Getty)

Despite the wall's intimidating nickname, both voyagers were able to pass through, with Voyager 1 crossing it in 2012, and Voyager 2 in 2018. Before the Voyager’s passed, the researchers were unsure where the boundary would be. However, since the probes hit it at different distances, the researchers learned more about it. Nasa said: ‘Scientists expected that the edge of the heliosphere, called the heliopause, can move as the Sun's activity changes, sort of like a lung expanding and contracting with breath. This was consistent with the fact that the two probes encountered the heliopause at different distances from the Sun' (Picture: Getty)

How did they make it through the extreme temperatures?

You might expect a 'wall of fire' to destroy anything that comes into its path. However, both Voyager 1 and Voyager 2 survived because the 'wall' is found in a particle-sparse region of space, meaning the chances of collision is very low and the heat wasn't able to transfer to Nasa's crafts (Picture: Getty Images)

Where is the edge of the solar system?

There is a debate about where the solar system ends. Some say it is where the planets end past Neptune. Others say it’s the end of the Kuiper belt, while some say it ends at the Oort cloud – the boundary of the Sun's gravitational influence. However, one way to define it would be where the Sun’s magnetic field ends, and pushes up against another interstellar medium, known as the heliosphere (Picture: Getty)

Nasa explains

Nasa says: ‘The Sun sends out a constant flow of charged particles called the solar wind, which ultimately travels past all the planets to some three times the distance to Pluto before being impeded by the interstellar medium. This forms a giant bubble around the Sun and its planets, known as the heliosphere. The boundary between solar wind and interstellar wind is the heliopause, where the pressure of the two winds are in balance. This balance in pressure causes the solar wind to turn back and flow down the tail of the heliosphere. As the heliosphere plows through interstellar space, a bow shock forms, similar to what forms as a ship plowing through the ocean’ (Picture: Getty)

Beyond the wall

It has been just under 50 years since the Voyager twins were launched, and so far they are the only two spacecrafts to have passed the 'wall'. They since have revealed several surprises, such as discovering the plasma in interstellar space is denser and colder than within the heliosphere. They also found a ‘magnetic highway’ where particles can flow in and out of the heliosphere (Picture: Getty)