About

Orbital mechanics errors compound. A 1% miscalculation in angular velocity places Mars 2.28 million km off-target after one orbit. This tool renders all 8 planets of the Solar System using Keplerian circular orbit approximations with real period ratios derived from NASA/JPL ephemeris data. Orbital radii use a compressed power function (r^0.6) and planet sizes use logarithmic scaling so that Mercury (2,440 km radius) and Jupiter (69,911 km) both remain visible without losing relative ordering. The simulation assumes circular orbits (eccentricity e = 0), which introduces <7% error for Mercury and <1% for most other planets.

Time scaling maps 1 Earth year to approximately 30 seconds at default speed. Click any planet to inspect its physical data. The asteroid belt is procedurally generated as a statistical distribution between 2.2 and 3.2 AU. All orbital periods are normalized against Earth's 365.25-day sidereal year. This is an approximation tool, not an ephemeris. For mission-critical trajectory planning, use JPL Horizons.

Formulas

Each planet's angular position at time t is computed from its sidereal orbital period T using the mean anomaly for circular orbits:

θ(t) = 2πT ⋅ t

Cartesian screen coordinates for each planet follow from polar-to-Cartesian conversion with a display scaling factor s and zoom factor z:

x = s ⋅ z ⋅ r^0.6 ⋅ cos(θ)

y = s ⋅ z ⋅ r^0.6 ⋅ sin(θ)

The power exponent 0.6 compresses the vast distance ratio between Mercury (0.387 AU) and Neptune (30.07 AU) into a viewable range. Planet display radii use logarithmic scaling:

R_display = R_min + k ⋅ ln(R_actual)

Where θ = angular position (rad), T = orbital period (days), t = elapsed simulation time, r = semi-major axis (AU), s = base pixel scale factor, z = user zoom level, R_min = minimum display radius (3 px), k = logarithmic scaling constant.

Reference Data

Planet	Orbital Radius (AU)	Orbital Period (days)	Equatorial Radius (km)	Mass (10²⁴ kg)	Surface Gravity (m/s²)	Moons	Avg Temp (°C)	Orbital Velocity (km/s)	Eccentricity
Mercury	0.387	87.97	2,440	0.330	3.70	0	167	47.36	0.2056
Venus	0.723	224.70	6,052	4.869	8.87	0	464	35.02	0.0068
Earth	1.000	365.25	6,371	5.972	9.81	1	15	29.78	0.0167
Mars	1.524	686.98	3,390	0.642	3.72	2	−65	24.07	0.0934
Jupiter	5.203	4,332.59	69,911	1,898	24.79	95	−110	13.07	0.0489
Saturn	9.537	10,759.22	58,232	568.3	10.44	146	−140	9.68	0.0565
Uranus	19.191	30,688.50	25,362	86.81	8.87	28	−195	6.80	0.0457
Neptune	30.069	60,182.00	24,622	102.4	11.15	16	−200	5.43	0.0113
Sun (star)	0	-	695,700	1,989,000	274.0	-	5,500 (surface)	-	-
Pluto (dwarf)	39.482	90,560.00	1,188	0.0130	0.62	5	−230	4.67	0.2488
Moon (Earth)	0.00257 (from Earth)	27.32	1,737	0.0735	1.62	0	−20	1.02	0.0549
Io (Jupiter)	0.00282 (from Jupiter)	1.77	1,822	0.0894	1.80	0	−143	17.33	0.0041
Europa (Jupiter)	0.00449 (from Jupiter)	3.55	1,561	0.0480	1.31	0	−160	13.74	0.0094
Titan (Saturn)	0.00817 (from Saturn)	15.95	2,575	0.1345	1.35	0	−179	5.57	0.0288

Frequently Asked Questions

A linear size mapping would render Mercury as a sub-pixel dot and Jupiter would dominate the entire canvas. The tool uses logarithmic radius scaling: R_display = R_min + k · ln(R_actual). This preserves the relative size ordering (Jupiter > Saturn > Uranus > Neptune > Earth > Venus > Mars > Mercury) while keeping all bodies visible. The trade-off is that size ratios are compressed by approximately 70%.

Orbital periods use NASA/JPL sidereal period values accurate to 4 significant figures. Mercury completes its orbit in 87.97 days and Neptune in 60,182 days. The ratio between any two planets' periods matches reality within 0.1%. However, orbits are assumed circular (eccentricity = 0), which introduces positional error up to 20% for Mercury (e = 0.2056) and less than 2% for Venus through Neptune.

Neptune orbits at 30.07 AU while Mercury orbits at 0.387 AU - a 78:1 ratio. At true scale, if Mercury were 10 pixels from the Sun, Neptune would be 780 pixels away, pushing it off most screens while the inner planets cluster into an indistinguishable clump. The power compression r^0.6 reduces this to a roughly 10:1 visual ratio, keeping all orbits distinguishable.

No. This is a Keplerian two-body approximation where each planet interacts only with the Sun. N-body gravitational perturbations (Jupiter's effect on asteroid orbits, Saturn-Jupiter resonances) are not modeled. For timescales under 1,000 years, the positional error from ignoring perturbations is under 0.5° for most planets. For longer timescales or mission planning, use numerical integrators like JPL Horizons.

At 1× speed, 1 Earth year maps to approximately 30 seconds of animation. The slider ranges from 0.1× (1 year = 5 minutes, useful for watching inner planet detail) to 50× (1 year = 0.6 seconds, useful for observing Neptune complete an orbit in about 100 seconds). The simulation accumulates elapsed time in fractional Earth-days regardless of frame rate, ensuring consistent physics even if rendering drops below 60 fps.

The asteroid belt contains 300 particles positioned between 2.2 and 3.2 AU using a seeded pseudo-random distribution. Each particle has a fixed random orbital radius, initial angle, and a period computed from Kepler's third law (T² ∝ r³). The particles orbit at physically correct relative speeds. The Kirkwood gaps at 2.5 AU (3:1 Jupiter resonance) are approximated by reducing particle density in that band.