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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.
That moment, called aphelion, will occur when the distance between the two celestial bodies stretches to more than 94.5 million miles. At perihelion, Earth is roughly 91.4 million miles away from ...
In modern times, Earth's perihelion occurs around January 3, and the aphelion around July 4. In other words, the Earth is closer to the Sun in January, and further away in July, which might seem counter-intuitive to those residing in the northern hemisphere, where it is colder when the Earth is closest to the sun and warmer when it is furthest ...
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]
Perihelion presently occurs around 3 January, while aphelion is around 4 July. When the orbit is at its most eccentric, the amount of solar radiation at perihelion will be about 23% more than at aphelion.
For Earth, orbital eccentricity e ≈ 0.016 71, apoapsis is aphelion and periapsis is perihelion, ... the seasons that occur on the far side of the orbit ...
Afternoon analemma photo taken in 1998–99 in Murray Hill, New Jersey, U.S., by Jack Fishburn.The Bell Laboratories building is in the foreground. In astronomy, an analemma (/ ˌ æ n ə ˈ l ɛ m ə /; from Ancient Greek ἀνάλημμα (analēmma) 'support') [a] is a diagram showing the position of the Sun in the sky as seen from a fixed location on Earth at the same mean solar time over ...
Tetrads occur when four lunar eclipses occur at four lunar inex numbers, decreseing by 8 (that is, a semester apart), which are in the range giving fairly central eclipses (small gamma), and furthermore the eclipses take place around halfway between the Earth's perihelion and aphelion.