The heliocentric model is the astronomical description of the solar system in which the Sun occupies a position at or near the center, with the Earth and other planets orbiting around it. The term is generally used in contrast to the geocentric (Ptolemaic) model, which places the Earth at the center with the Sun, Moon, planets, and stars revolving around it. Within modern astrophysics the heliocentric model is understood as a simplification: the Sun itself orbits the barycenter of the solar system and the galactic center, but for the purposes of describing planetary motion within the solar system, “heliocentric” remains the standard operational term.
The heliocentric model, in its modern Keplerian-Newtonian form, is the framework used throughout contemporary astronomy, physics, and space navigation. Planets are described as following elliptical orbits with the Sun at one focus, governed by Newtonian gravitation and, where precision requires it, general relativity (as in the perihelion precession of Mercury). Spacecraft trajectory calculations, satellite positioning, and stellar parallax measurements-such as those obtained for nearby stars including 61 Cygni, whose parallax was first measured by Friedrich Bessel in 1838-rely on and independently corroborate a heliocentric (more precisely, barycentric) reference frame.
Historically, the model's acceptance was not instantaneous; the transition from geocentric to heliocentric astronomy spanned roughly a century and involved observational, theological, and philosophical disputes, as documented by Kuhn and by Gingerich. For fuller historical treatment, see heliocentric-model-history.
A residual philosophical point recurs in discussions of the model: in general relativity, no reference frame is privileged, so “the Earth orbits the Sun” and “the Sun orbits the Earth” are both describable, with the heliocentric frame preferred for its simpler equations of motion; see heliocentric-model-frame-of-reference-debate and Viewpoints below.
There is broad, independent consensus across astronomy, physics, and the space sciences that the heliocentric (more precisely heliocentric-barycentric) model correctly describes the kinematics of the solar system, and that this consensus rests on multiple independent lines of evidence-stellar parallax, stellar aberration, Foucault pendulum demonstrations, Newtonian and relativistic gravitational mechanics, and direct spacecraft observation. See heliocentric-model-consensus.