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Sun-Earth Distance You may use the keys y, m, d, h to increase the year, month, day, or hour, or shift key and y, m, d, h to decrease the year, month, day, or hour. Click into the applet area first ! Click the applet area first. Then: enter decimal degree values for Latitude (southern negative) into the text field of the applet, and press Enter key, enter decimal degree values for Longitude (western negative) into the text field of the applet, and press Enter key. Latitude 51.51, Longitude 13.41 is Berlin/Germany. Select from the "Details" menu to get a data table or different diagrams. The applet is computing the distance of the Earth from the Sun (kilometers and Astronomical Units) using the 180 most important of 997 terms from the VSOP87 planetary theory. The accuracy of the Sun-Earth distance better than +/- 5·10-7 AU = 75 km, using the conversion 1 AU = 149,597,870 km. The times of perihelion and aphelion are accurate within about 0.5 hour. The right ascension and the declination (using fewer terms) are accurate within about 1''. Select "Anomalistic" from the "Details" menu: Select "Data Table" from the "Details" menu: Perihelion 2011 occurs on Jan 3 at 19 UT (0.9833412 AU). Geocentric perihelion distance 2010 - 2026 computed by MICA (Multiyear Interactive Computer Almanac by US Naval Observatory) 2010 - 2026 Distance / AU Distance / km Mean 0.983,299,155 147.099,459 Minimum 0.983,243,565 147,091,143 Maximum 0.983,341,273 147,105,760 Max. - Min. 0,000,097,708 14,617 (Max-Min)/Mean 0.010 % Stand. Dev. 0.000,026,692 3.993 Stand. Dev. 0.0029 % The small perihelion distance of the Earth in 2020 and 2021 is due to the conjunctions of Jupiter with the Sun (2019 Dec 27, 2021 Jan 29). Perihelion occurs between Jan 2  and Jan 05 (mean date is Jan 4.0): 2010 - 2026 Anomalistic Year / days Mean 365.294 Minimum 363.167 Maximum 367.625 Max. - Min. 4.458 (Max-Min)/Mean 1.22 % Stand. Dev. 1.636 Stand. Dev. 0.45 % The ecliptical longitude of the perihelion is advancing by about 3.3° from 1900 to 2100, making one complete cycle in 22,000 to 26,000 years: 2000 - 2050 excentricity Mean 0.0166988 Minimum 0.0166584 Maximum 0.0167521 Max. - Min. 0.000094 (Max-Min)/Mean 0.56 % Stand. Dev. 0.000021 Stand. Dev. 0.13 % The eccentricity of the Earth's orbit 1900 - 2100 according to Meeus (Astronomical Algorithms, Willmann-Bell) is decreasing by 0.000,042 per century (0.0167,086 in 2000). In 29,450 there will be a minimum of 0.002281: More details about long-period variation of the Earth's eccentricity Select "Difference" from the "Details" menu: Showing the second differences dn of daily distances rn: dn = (rn+1 - rn) - (rn - rn-1) = rn+1 - 2rn + rn-1 which is an approximation of the second derivative of the r(t) function. It is about zero near the equinoxes where the orbit is almost circular (dn=0). The local minima of dn occur at New Moon. Select "Orbit" from the "Details" menu: An eccenticity of 0.0167 and a radius of 380 pix yields a difference between perihelion and aphelion distance of 12 pix. Marks for the date of the month: This checkboxes is showing the magnified radius (magenta), concentric gray circles at 0.995 AU, 1 AU, and 1.005 AU The local radius (cyan) is computed from 3 adjacent points Pn-1, Pn, Pn+1, using rectangular coordinates computed from the radius r and the ecliptical longitude L. Cyclic variations is due to the Eart's moon. Local minima occur at new moon.

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Year (Wikipedia) Apsis (Wikipedia) Secular variations of the planetary orbits (Wikipedia)

© 2011 J. Giesen

Last modified: 2011 Mar 15