Sedna's Detached Orbit & the Inner Oort Cloud

Your Object's Orbit

Semi-major axis a 90 AU

Eccentricity e 0.75

Inclination i 15°

Time scale 150 yr/s

Presets

Live Readouts

Perihelion q

22.5 AU

Aphelion Q

157.5 AU

Orbital period T

854 yr

Current heliocentric distance r

— AU

Coupled to Neptune (scatterable)

How it works

Every body here follows a true Keplerian ellipse with the Sun at one focus. Position is found by solving Kepler's equation for the eccentric anomaly E from the mean anomaly M = 2π·t/T (Newton–Raphson), then converting to Cartesian coordinates:

M(t) = M0 + 2π t / T          T = a^1.5  (years, a in AU, solar mass)
E - e·sinE = M                (solved numerically each frame)
x = a(cosE - e)
y = a·sqrt(1-e²)·sinE
q = a(1-e)   perihelion        Q = a(1+e)   aphelion

The detachment puzzle: Neptune (a ≈ 30 AU) can gravitationally scatter any object whose perihelion dips within roughly its own orbit — that's the "scattered disk," objects with q near 30–40 AU that get kicked around every close pass. Sedna (q ≈ 76 AU, a ≈ 506 AU) and 2012 VP113 (q ≈ 80 AU) are different: their perihelia sit far *outside* Neptune's reach, so nothing in the known Solar System can have put them there or can currently perturb them. They are dynamically detached.

a, e sliders — set your test object's semi-major axis and eccentricity; q and Q update live, and the badge flips between "coupled" and "detached" at the q ≈ 40 AU threshold used in the literature.
Inclination slider — tilts the orbital plane, matching how real detached objects have large, scattered inclinations (a signature of past dynamical stirring).
Time scale — because periods range from ~250 years (classical Kuiper belt) to over 11,000 years (Sedna), this compresses simulated time so orbits are watchable.

Leading explanations for detached orbits: a passing star during the Sun's birth cluster tugging perihelia outward, an undiscovered distant "Planet Nine," or a stellar flyby raising perihelion after formation in the scattered disk. No single mechanism is confirmed — it remains an open question in Solar System dynamics.

Sun Neptune (a≈30 AU) Classical KBO Your object

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