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The eccentricity of Earth's orbit is currently about 0.016 7; its orbit is nearly circular. Neptune's and Venus's have even lower eccentricities of 0.008 6 and 0.006 8 respectively, the latter being the least orbital eccentricity of any planet in the Solar System.
The Earth's orbit varies between nearly circular and mildly elliptical (its eccentricity varies). When the orbit is more elongated, there is more variation in the distance between the Earth and the Sun, and in the amount of solar radiation, at different times in the year.
One complete orbit takes 365.256 days (1 sidereal year), during which time Earth has traveled 940 million km (584 million mi). [2] Ignoring the influence of other Solar System bodies, Earth's orbit, also called Earth's revolution, is an ellipse with the Earth–Sun barycenter as one focus with a current eccentricity of 0.0167. Since this value ...
The eccentricity ε is the coefficient of variation between r ... so the eccentricity of the orbit of the Earth is ... an ellipse can be represented by the formula:
Orbital forcing is the effect on climate of slow changes in the tilt of the Earth's axis and shape of the Earth's orbit around the Sun (see Milankovitch cycles).These orbital changes modify the total amount of sunlight reaching the Earth by up to 25% at mid-latitudes (from 400 to 500 W/(m 2) at latitudes of 60 degrees).
As a result, the eccentricity of the Earth's orbit contributes a periodic variation which is (in the first-order approximation) a sine wave with: amplitude: 7.66 minutes; period: one year; zero points: perihelion (at the beginning of January) and aphelion (beginning of July) extreme values: early April (negative) and early October (positive)
In the case of Mercury, half of the greater axis is about 5.79 × 10 10 m, the eccentricity of its orbit is 0.206 and the period of revolution 87.97 days or 7.6 × 10 6 s. From these and the speed of light (which is ~ 3 × 10 8 m/s ), it can be calculated that the apsidal precession during one period of revolution is ε = 5.028 × 10 −7 ...
Due to the very slow pole motion of the Earth, the Celestial Ephemeris Pole (CEP, or celestial pole) does not stay still on the surface of the Earth.The Celestial Ephemeris Pole is calculated from observation data, and is averaged, so it differs from the instantaneous rotation axis by quasi-diurnal terms, which are as small as under 0.01" (see [6]).