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The ancient Greek astronomer Hipparchus noted the apsidal precession of the Moon's orbit (as the revolution of the Moon's apogee with a period of approximately 8.85 years); [4] it is corrected for in the Antikythera Mechanism (circa 80 BCE) (with the supposed value of 8.88 years per full cycle, correct to within 0.34% of current measurements). [5]
The apsides refer to the farthest (2) and nearest (3) points reached by an orbiting planetary body (2 and 3) with respect to a primary, or host, body (1). An apsis (from Ancient Greek ἁψίς (hapsís) 'arch, vault'; pl. apsides / ˈ æ p s ɪ ˌ d iː z / AP-sih-deez) [1] [2] is the farthest or nearest point in the orbit of a planetary body about its primary body.
An object with an e of between 0 and 1 will have an elliptical orbit, with, for instance, an object with an e of 0.5 having a perihelion twice as close to the Sun as its aphelion. As an object's e approaches 1, its orbit will be more and more elongated before, and at e =1, the object's orbit will be parabolic and unbound to the Solar System (i ...
The Earth spends less time near perihelion and more time near aphelion. This means that the lengths of the seasons vary. [ 14 ] Perihelion currently occurs around 3 January, so the Earth's greater velocity shortens winter and autumn in the northern hemisphere, and summer and spring in the southern hemisphere.
Most sungrazing comets are part of the Kreutz family. [8] The group generally has an eccentricity approaching 1, [9] orbital inclination of 139–144° (precluding close encounters with planets), [10] a perihelion distance of less than 0.01 AU (less than the diameter of the Sun [11]), an aphelion distance of about 100 AU [12] and an orbital period of about 500–1,000 years. [4]
The nominal best-fit orbit solution provided by the Jet Propulsion Laboratory (JPL) Small-Body Database gives an orbital semi-major axis of 80.2 ± 4.5 AU and an eccentricity of 0.655 ± 0.02, corresponding to a perihelion and aphelion distance of 27.6 ± 0.2 AU and 133 ± 7 AU, respectively.
The orbital perihelion of these objects is close to, but greater than, the orbital aphelion of Earth (i.e., the objects do not cross Earth's orbit), [1] with most Amors crossing the orbit of Mars. The Amor asteroid 433 Eros was the first asteroid to be orbited and landed upon by a robotic space probe ( NEAR Shoemaker ).
2012 VP 113 is the minor planet with the farthest known perihelion (closest approach to the Sun) in the Solar System, greater than Sedna's. [13] Though its perihelion is farther, 2012 VP 113 has an aphelion only about half of Sedna's. It is the second discovered sednoid, with semi-major axis beyond 150 AU and perihelion greater than 50 AU.