Pronunciation: [ɐfˈɛli͡ən] (IPA) 
Aphelion is a term used to describe the point in the orbit of a planet or other celestial body where it is farthest from the sun. The spelling of Aphelion is phonetically pronounced as /æˈfiːliən/ ah-FEE-lee-ən. The "ph" in the word is silent, and the first vowel sound is pronounced "ah" rather than "ay." The spelling of this word can sometimes confuse people due to its uncommon use and phonetic irregularities.
Aphelion is a term used in astronomy to describe the farthest point of a celestial object's orbit from the Sun. Specifically, it refers to the point of maximum separation between a planet or comet and the Sun in its elliptical orbit. Derived from the Greek words "apo" meaning "away from" and "helios" meaning "Sun," aphelion is the opposite of perihelion, which designates the closest point of an object's orbit to the Sun.
The distance between a celestial body and the Sun is not constant due to the elliptical nature of their orbits. Therefore, the aphelion is a significant astronomical measure as it represents the point where the object is at its greatest distance from the Sun. For instance, in the case of planets in our solar system, Earth's aphelion occurs around July 4th and is approximately 152 million kilometers (94.5 million miles) away from the Sun. In contrast, Mars reaches its aphelion at around the beginning of November, with a distance of about 249 million kilometers (147 million miles) separating it from the Sun.
Understanding the concept of aphelion is vital in studying celestial mechanics, planetary motions, and the dynamics of space. It plays a crucial role in determining various astronomical phenomena, such as the peak temperature difference between seasons on a planet, the occurrence of meteor showers, and the calculation of orbital periods and velocities of celestial objects.
The position of a planet in the heavens when farthest from the sun-when nearest to the sun, the position is called its perihelion.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.
The word "aphelion" is derived from the combination of two Greek words: "apo" meaning "away from" and "helios" meaning "sun". "Aphelion" specifically refers to the point in an orbit around the sun when the distance between the sun and a celestial object (such as a planet) is at its greatest.
