Any system of coordinates with their origin at the centre of the Sun. They are often used for describing the positions of bodies in the Solar System. They can be either spherical coordinates or rectangular coordinates. Heliocentric spherical coordinates are given in terms of heliocentric latitude and heliocentric longitude. A variant system, barycentric coordinates, gives positions referred to the centre of mass of the Solar System (the barycentre), which is slightly displaced from the centre of the Sun.