What does anthelion mean?
An anthelion is a rare atmospheric optical phenomenon that appears as a faint, diffuse, whitish spot of light directly opposite the sun in the sky — that is, at the antisolar point, the position exactly 180 degrees from the sun as seen by the observer. It belongs to the same family of ice-crystal phenomena as halos and sundogs, forming when sunlight is reflected by airborne ice crystals, often in thin clouds or diamond dust. Unlike the brighter, more colorful parhelions (sundogs) that flank the sun itself, an anthelion is subtle and easily overlooked, which makes sightings relatively uncommon and prized by atmospheric-optics enthusiasts and photographers, particularly when viewed from aircraft. The word derives from Greek roots meaning 'opposite the sun', and its plural form is anthelia. Though specialized, the term offers a precise name for one of the sky's most elusive displays of light.
nounA rare atmospheric optical phenomenon appearing as a faint, diffuse white spot of light directly opposite the sun in the sky, at the antisolar point; it resembles a parhelion (sundog) but occurs on the side of the observer away from the sun.
- A rare halo-like optical phenomenon consisting of a faint white spot of light at the antisolar point, directly opposite the sun.
"As the sun sank behind them, the climbers noticed a pale anthelion glowing on the horizon ahead."
"The pilot reported an unusual anthelion visible below the horizon line during the evening flight."
"Photographers sometimes capture an anthelion from aircraft, where the phenomenon appears against clouds beneath them."
The standard plural follows the Latinized Greek pattern used for other '-ion' astronomical and optical terms; 'anthelions' also appears in some modern sources.
"Observers at high altitude occasionally report anthelia accompanying complex halo displays."
An anthelion is a ghostly patch of light that appears exactly where the sun can never be — directly opposite it in the sky.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of anthelion
The word anthelion comes from Greek, combining 'anti-' (against, opposite) with 'helios' (sun), literally meaning 'opposite the sun'. It entered English usage in the context of natural philosophy and meteorology, alongside related terms such as parhelion, which shares the same root 'helios'. The Greek solar root also gave English words such as helium, heliocentric, and heliotrope, all of which preserve the ancient association with the sun.
How anthelion is actually used
A technical term used almost exclusively in meteorology, atmospheric optics, and scientific writing; rarely encountered in everyday speech. It is always countable and typically takes the plural 'anthelia'.
Easily confused with anthelion
A parhelion (sundog) appears beside the sun as bright colored spots, while an anthelion appears directly opposite the sun and is typically a faint, whitish glow.