aphelion

noun

plural aphelia a-ˈfēl-yə How to pronounce aphelion (audio)
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

Recent Examples on the Web 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 For the next six months or so, our planet will slowly move away from the sun, reaching its most distant point—aphelion—on July 5. Phil Plait, Scientific American, 5 Jan. 2024 The exact distances of Earth’s perihelion and aphelion change a bit from year to year because of the gravitational influence of the other planets, as well as that of the moon. Phil Plait, Scientific American, 30 June 2023 Once every 12 months, the Earth reaches what is known as its aphelion—or furthest approach—drifting out to about 150 million km (94.5 million mi.). Jeffrey Kluger, Time, 21 July 2023 Called aphelion, this moment will occur on July 6 at 4 P.M. EST at a distance of 94,506,364 miles. Michael D'estries, Treehugger, 30 June 2023 But as of 2023’s aphelion, Earth’s center will be 152,093,250 kilometers from the center of the sun. Phil Plait, Scientific American, 30 June 2023 These are from aphelion and perihelion in 2005, but the scale is always about the same every year. Phil Plait, Discover Magazine, 5 July 2012

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'aphelion.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

New Latin, from apo- + Greek hēlios sun — more at solar

First Known Use

1656, in the meaning defined above

Time Traveler
The first known use of aphelion was in 1656

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Cite this Entry

“Aphelion.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/aphelion. Accessed 21 Jun. 2024.

Kids Definition

aphelion

noun
aph·​elion a-ˈfēl-yən How to pronounce aphelion (audio)
plural aphelia -yə How to pronounce aphelion (audio)
: the point in the orbit of a heavenly body (as a planet) that is farthest from the sun

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