火星轨道

火星轨道的半长轴为1.524天文單位（2.28亿公里），偏心率为0.0934Jean Meeus, Astronomical Formulæ for Calculators. (Richmond, VA: Willmann-Bell, 1988) 99. Elements by F. E. Ross。这颗行星绕太阳一圈需要687天In ephemeris days of 86 400 seconds. The sidereal and anomalistic years are 686.980 days and 686.996 days long, respectively. (About a 20 minute difference). The sidereal year is the time taken to revolve around the Sun relative to a fixed reference frame. More precisely, the sidereal year is one way to express the rate of change of the mean longitude at one instant, with respect to a fixed equinox. The calculation shows how long it would take for the longitude to change 360 degrees at the given rate.
The anomalistic year is the time span between successive perihelion or aphelion passages. This may be calculated in the same manner as the sidereal year, but the mean anomaly is used.，绕太阳一圈的里程为9.55天文单位Jean Meeus, Astronomical Algorithms (Richmond, VA: Willmann-Bell, 1998) 238. The formula by Ramanujan is accurate enough.，平均轨道速度为24公里/秒。

参考文献

Category:火星
Category:太陽系動力學