Heliocentric orbit

Short description: Orbit around the barycenter of the Sun

"Solar orbit" redirects here. For the orbit of the Sun, see Sun § Motion.

Motion of the Solar System's barycenter relative to the Sun

A heliocentric orbit (also called circumsolar orbit) is an orbit around the Sun. The inner planets are mainly influenced by the Sun's gravity, and orbit points close to the center of the Sun ('heliocentric' in a strict sense). The outer planets, and other more distant objects, tend to orbit points close to the barycenter of the Solar System, which is usually located within or very near the surface of the Sun. Comets which traverse the inner Solar System shift between a nearly heliocentric focus, when they are close to the Sun, and a nearly barycentric one when they are more distant than Jupiter. [1] All planets, comets, and asteroids in the Solar System, and the Sun itself 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 (although the Moon has a convex orbit around the Sun).

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 giants, are located at that time. A similar phenomenon allows the detection of exoplanets by way of the radial-velocity method.

The helio- prefix is derived from the Greek word "ἥλιος", meaning "Sun", and also Helios, the personification of the Sun in Greek mythology.[2]

The first spacecraft to be put in a heliocentric orbit was Luna 1 in 1959. An incorrectly timed upper-stage burn caused it to miss its planned impact on the Moon.[3]

## Trans-Mars injection

Trans-Mars injection diagram.
A = Hohmann transfer orbit. B = Conjunction mission. C = Opposition mission

A trans-Mars injection (TMI) is a heliocentric orbit in which a propulsive maneuver is used to set a spacecraft on a trajectory, also known as Mars transfer orbit, which will place it as far as Mars orbit.

Every two years, low-energy transfer windows open up, which allow movement between the two planets with the lowest possible energy requirements. Transfer injections can place spacecraft into either a Hohmann transfer orbit or bi-elliptic transfer orbit. Trans-Mars injections can be either a single maneuver burn, such as that used by the NASA MAVEN orbiter in 2013, or a series of perigee kicks, such as that used by the ISRO Mars Orbiter Mission in 2013.[4][5]

## See also

* Astrodynamics
* Earth's orbit
* Geocentric orbit
* Heliocentrism
* List of artificial objects in heliocentric orbit
* List of orbits
* Low-energy transfer

## References

1. ↑ "Sun Close-Encounter model of Long-Period Comet and Meteoroid Orbit Stochastic Evolution". Icarus (Elsevier) 437. September 2025. https://www.sciencedirect.com/science/article/abs/pii/S001910352500106X. Retrieved 2026-03-04.
2. ↑ "helio-". Dictionary.com Unabridged (v 1.1). Random House. 2006. http://dictionary.reference.com/browse/helio-.
3. ↑ "NASA – NSSDCA – Spacecraft – Details". https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1959-012A.
4. ↑ ISRO successfully sends Mars orbiter into sun-centric orbit.
5. ↑ Orbiter successfully placed in Mars Transfer Trajectory.

* v
* t
* e

Gravitational orbits

Types|

| General|

* Box
* Capture
* Circular
* Elliptical / Highly elliptical
* Escape
* Horseshoe
* Hyperbolic trajectory
* Inclined / Non-inclined
* Lagrangian point
* Osculating
* Parabolic trajectory
* Parking
* Prograde / Retrograde
* Synchronous
* semi
* sub
* Transfer orbit

|

Geocentric|

* Geosynchronous
* Geostationary
* Geostationary transfer
* Graveyard
* High Earth
* Low Earth
* Medium Earth
* Molniya
* Near-equatorial
* Orbit of the Moon
* Polar
* Sun-synchronous
* Tundra

About other points|

* Mars
* Areosynchronous
* Areostationary
* Lagrange points
* Distant retrograde
* Halo
* Lissajous
* Lunar
* Sun
* Heliocentric
* Earth's orbit
* Heliosynchronous

Parameters|

* Shape
* Size

* e Eccentricity
* a Semi-major axis
* b Semi-minor axis
* Q, q Apsides

|

Orientation|

* i Inclination
* Ω Longitude of the ascending node
* ω Argument of periapsis
* ϖ Longitude of the periapsis

Position|

* M Mean anomaly
* ν, θ, f True anomaly
* E Eccentric anomaly
* L Mean longitude
* l True longitude

Variation|

* T Orbital period
* n Mean motion
* v Orbital speed
* t0 Epoch

Maneuvers|

* Bi-elliptic transfer
* Collision avoidance (spacecraft)
* Delta-v
* Delta-v budget
* Gravity assist
* Gravity turn
* Hohmann transfer
* Inclination change
* Low energy transfer
* Oberth effect
* Phasing
* Rocket equation
* Rendezvous
* Transposition, docking, and extraction

Orbital mechanics|

* Celestial coordinate system
* Characteristic energy
* Escape velocity
* Ephemeris
* Equatorial coordinate system
* Ground track
* Hill sphere
* Interplanetary Transport Network
* Kepler's laws of planetary motion
* Lagrangian point
* n-body problem
* Orbit equation
* Orbital state vectors
* Perturbation
* Retrograde motion
* Specific orbital energy
* Specific relative angular momentum
* Two-line elements

* List of orbits

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