The Planets

by Dominic Ford, Editor

Physical characteristics of the planets

Planet Mass (Earth masses)Radius (Earth radii)Mean distance from Sun (AU)Orbital period
Mercury 0.055 0.3829 0.387 88 days
Venus 0.815 0.950 0.723 225 days
Earth 1 1 1 365.2564 days
Mars 0.107 0.532 1.524 687 days
Jupiter 317.8 10.96 5.204 11.862 yrs
Saturn 95.152 9.4492 9.582 29.46 yrs
Uranus 14.54 4.01 19.23 84.3 yrs
Neptune 17.147 3.883 30.10 164.8 yrs

Orbital elements of the planets

Below are osculating elements for the planets, given for epoch 2000 January 1.5 (i.e. Julian Day 2451545.0).

The elements are a least-squares fit to the 250-year span of the DE 200 planetary ephemeris to a Keplerian orbit, where each element is allowed to vary linearly with time. The resulting elements fit the positions of the terrestrial planets to within 25 arcseconds or better, but achieves only 10-arcminute accuracy for Saturn. Elements are referenced to mean ecliptic and equinox of J2000 at the J2000 epoch (2451545.0 JD).

Planet Semimajor axis
(AU)
Eccentricity Inclination
degrees
Longitude of
Ascending Node

degrees
Argument of
perihelion

degrees
Mean anomaly
at epoch

degrees
Mercury 0.38709893 0.20563069 7.00487 48.33167 29.12478 174.79439
Venus 0.72333199 0.00677323 3.39471 76.68069 54.85229 50.44675
Mars 1.52366231 0.09341233 1.85061 49.57854 286.46230 19.41248
Jupiter 5.20336301 0.04839266 1.30530 100.55615 -85.80230 19.65053
Saturn 9.53707032 0.05415060 2.48446 113.71504 -21.28310 -42.48762
Uranus 19.19126393 0.04716771 0.76986 74.22988 96.73436 142.26794
Neptune 30.06896348 0.00858587 1.76917 131.72169 -86.75034 259.90868

Derivatives of the orbital elements of the planets

Planet Semimajor axis
AU/Cyr
Eccentricity
/Cyr
Inclination
deg/Cyr
Longitude of
Ascending Node

deg/Cyr
Argument of
perihelion

deg/Cyr
Mean anomaly
deg/Cyr
Mercury 0.00000066 0.00002527 -0.00653 -0.12397 0.28330 149472.51520
Venus 0.00000092 -0.00004938 -0.00079 -0.27691 0.24669 58517.84579
Mars -0.00007221 0.00011902 -0.00707 -0.28339 0.71694 19139.87306
Jupiter 0.00060737 -0.00012880 -0.00115 0.33810 -0.10479 3034.51067
Saturn -0.00301530 -0.00036762 0.00170 -0.44196 -0.09940 1223.05607
Uranus 0.00152025 -0.00019150 -0.00058 -0.46706 0.83166 428.12090
Neptune -0.00125196 0.00002510 -0.00101 -0.04201 -0.19255 218.69268

Cyr = 1 Julian century (i.e. 36525 days)

References

Explanatory Supplement to the Astronomical Almanac. 1992. K. P. Seidelmann, Ed., p.316 (Table 5.8.1), University Science Books, Mill Valley, California.

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