The shield of our Solar System, the heliosphere, plays a crucial role in protecting the planets against the extremely energetic galactic cosmic rays. But how can we study it?
A future interstellar probe mission aims to travel beyond the heliosphere into the interstellar medium.
Credit: John Hopkins Applied Physics Laboratory
The heliosphere consists of the solar wind, solar transients, and the interplanetary magnetic field. These elements form a screen that protects against galactic cosmic particles, accelerated by events like supernovas. Without the heliosphere, these particles would cause huge damage to the planets.
However, the precise shape and boundaries of the heliosphere remain uncertain. Studies, such as the one led by the University of Michigan and published in Frontiers in Astronomy and Space Sciences, explore concepts for interstellar missions. These missions beyond the solar influence aim to understand the size and shape of our "home" from the outside.
The interactions of the heliosphere with the local interstellar medium, a material made up of plasma, dust, and neutral particles, determine the shape of our heliosphere and influence the composition of the space environment in the Solar System, including near Earth.
To date, the Voyager 1 and 2 probes are the only missions that have potentially left the heliosphere. The analysis of their trajectory and collected data underscores the importance of making new measurements outside the heliosphere to determine its definitive shape. Researchers recommend collecting scientific measurements on future missions to the edges of the heliosphere to better understand its interaction with the interstellar medium.
A 2021 mission concept highlighted the technical aspects of different trajectories for a future interstellar probe. Researchers conclude that a trajectory crossing the heliospheric flank at the level of "its potential tail" would offer the best perspective on the shape of the heliosphere and maximize scientific outcomes. Current models predict that the heliosphere could adopt a spherical, elongated, or crescent shape.
The Voyager probe, after a 46-year journey, has traveled about 163 astronomical units from Earth. In the future, an interstellar probe could be designed for a 50-year mission, aiming to travel about 400 astronomical units and could even reach up to 1,000 astronomical units, offering an unprecedented view of our heliosphere and the interstellar medium beyond.