22° halo
optical phenomenon visible around sun and moon in the earth athmosphere
A 22° halo is an atmospheric optical phenomenon that consists of a halo with an apparent radius of approximately 22° around the Sun or Moon. Around the Sun, it may also be called a sun halo. Around the Moon, it is also known as a moon ring, storm ring, or winter halo. It forms as sunlight or moonlight is refracted by millions of hexagonal ice crystals suspended in the atmosphere. Its radius, as viewed from Earth, is roughly the length of an outstretched hand at arm's length.
Formation
Even though it is one of the most common types of halo, the shape and orientation of the ice crystals responsible for the 22° halo are a topic of debate. Hexagonal, randomly oriented columns are usually put forward as the most likely candidate, but this explanation presents problems, such as the fact that the aerodynamic properties of such crystals lead them to be oriented horizontally rather than randomly. Alternative explanations include the involvement of clusters of bullet-shaped ice columns.
As light passes through the 60° apex angle of the hexagonal ice prisms, it is deflected twice, resulting in deviation angles ranging from 22° to 50°. Given the angle of incidence onto the hexagonal ice prism
θ
incidence
{\displaystyle \theta _{\text{incidence}}}
and the refractive index inside the prism
n
{\displaystyle n}
, then the angle of deviation
θ
deviation
{\displaystyle \theta _{\text{deviation}}}
can be derived from Snell's law:
θ
deviation
=
θ
incidence
+
sin
−
1
[
n
sin
(
π
3
−
sin
−
1
sin
θ
incidence
n
)
]
−
π
3
.
The public source identifies “22° halo” as optical phenomenon visible around sun and moon in the earth athmosphere. This brief keeps that definition visible, then builds a research path around halo, optical and phenomenon.
Why this record matters
A short description can identify a subject without explaining its stakes. For “22° halo”, the useful work is to connect “optical phenomenon visible around sun and moon in the earth athmosphere” to the records capable of establishing context and consequence.
The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Aug 2, 2026. The linked authority identifier is Q1771751. None of the 0 selected statements returned an explicit reference.
A concise general-reference account can conceal disagreements about scope, terminology or the weight assigned to individual sources. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Use the entry as an orientation point, then follow its citations and revision history. Names, dates and institutional relationships should be checked against the original record.
- Subject orientation
- Search vocabulary
- Locating named sources
The closest primary source, responsible institution and strongest cited specialist reference.
Three-step research path
- Establish the record: confirm the title “22° halo”, its source revision and the description used here.
- Expand the search: follow 22° halo primary sources, 22° halo archive and halo research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “22° halo”?
- Which cited source is closest to the event, object or claim?
- Which institution is responsible for the underlying evidence?
Search terms from this dossier
This entry incorporates text from “22° halo” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.