aphelion

noun

aph·elion a-ˈfēl-yən

ˌap-ˈhēl-

plural aphelia a-ˈfēl-yə

ˌap-ˈhēl-

: the point farthest from the sun in the path of an orbiting celestial body (such as a planet) compare perihelion

Did you know?

Aphelion and perihelion are troublesome terms. Which one means a planet is nearest to the sun and which means it is farthest away? An etymology lesson may help you keep those words straight. Just remember that the "ap" of aphelion derives from a Latin prefix that means "away from" (the mnemonic "'A' for 'away'" can help too); peri-, on the other hand, means "near." And how are aphelion and perihelion related to the similar-looking astronomical pair apogee and perigee? Etymology explains again. The "helion" of aphelion and perihelion is based on the Greek word hēlios, meaning "sun," while the "gee" of apogee and perigee is based on gaia, meaning "earth." The first pair describes distance in relation to the sun, the second in relation to the Earth.

Examples of aphelion in a Sentence

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Mars’s orbit is much more elliptical—with an aphelion, or furthest remove from the sun, of 155 million miles and a perihelion, or closest approach, of 128 million miles. —

Jeffrey Kluger, TIME, 6 Sep. 2024 At aphelion, water has an abundance of less than one part per million in Mars’s skies, compared to more than 50 parts per million at perihelion. —

Jeffrey Kluger, TIME, 6 Sep. 2024 Read More: How Animals and Nature React to an Eclipse Earth’s orbit around the sun is elliptical too, with a maximum distance, or aphelion, of about 152.1 million km (94.5 million mi.), and a minimum distance, or perihelion, of 147.1 million km (91.4 million mi.). —

TIME, 28 Mar. 2024 Due to its slightly elliptical orbit around the Sun, Earth will reach aphelion this year on July 5, at a distance of 94.5 million miles (152 million km). —

Eric Berger, Ars Technica, 4 Jan. 2024 See all Example Sentences for aphelion