The BepiColombo heliocentric cruise will use gravity assists around the Earth, Venus and Mercury and will last 6 years
A heliocentric orbit (also called circumsolar orbit) is an orbit around the barycenter of the Solar System, which is usually located within or very near the surface of the Sun. All planets, comets, and asteroids in our Solar System are in such orbits, as are many artificial probes and pieces of debris. The moons of planets in the Solar System, by contrast, are not in heliocentric orbits as they orbit their respective planet.
The barycenter of the Solar system, while always very near the Sun, moves through space as time passes depending on where other large bodies in the solar system, such as Jupiter and other large gas planets, are located at that time. A similar phenomenon allows the detection of extrasolar planets by way of the radial velocity method.