Anthelion

An anthelion (plural anthelia, from late Greek ανθηλιος, "opposite the sun") is a rare optical phenomenon of the halo family.

It appears on the parhelic circle opposite to the Sun as a faint white spot, not unlike a sundog, and may be crossed by an X-shaped pair of diffuse arcs.

[1] However, anthelia occur unaccompanied by other plate crystal haloes, thus scientists have produced alternative explanations.

[1] While the anthelion area is usually sparse on haloes, in a complex display it features various rare optic phenomena: Flanking the anthelion on the parhelic circle are two 120° parhelia (and two Liljequist parhelia) caused by plate crystals.

The Tricker and diffuse arcs are produced in singly oriented column crystals and form an ankh-like shape passing through the anthelion.