The slingshot effect, or gravity-assist manoeuvre is when a space probe approaches a celestial body, it will follow a symmetrical parabolic path in which its incomnig and outgoing speeds are the same. The probe will have been accelerated due to the gravitational acceleration of the body and accordingly, the conservation of energy will dictate that the celestial body will experience a force slowing it down as it loses kinetic energy. However, relative to the Sun, its speed will have increased since the probe acquires angular momentum from the planet as it loses angular momentum.