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Credit & Copyright: Christa Harbig
Explanation:
What's happening to this cloud?
Ice crystals in a distant cirrus cloud are acting like little floating
prisms.
Known informally as a fire rainbow for its flame-like appearance, a
circumhorizon arc
appears parallel to the horizon.
For a circumhorizontal arc
to be visible,
the Sun
must be at least 58 degrees high in a sky where
cirrus clouds present below
--
in this case
cirrus fibratus.
The numerous, flat,
hexagonal ice-crystals
that compose the
cirrus cloud must be
aligned horizontally
to properly
refract sunlight in a collectively
similar manner.
Therefore, circumhorizontal
arcs are
somewhat
unusual to see.
The featured fire rainbow was photographed in 2021 near
North Fork Mountain in
West Virginia,
USA.
Sky Surprise:
What picture did APOD feature on your birthday? (after 1995)
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NASA Web Site Statements, Warnings, and Disclaimers
NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
Based on Astronomy Picture
Of the Day
Publications with keywords: clouds
Publications with words: clouds
See also:
- APOD: 2026 January 6 Á Jupiters Clouds in High Definition from Juno
- APOD: 2025 August 17 Á Asperitas Clouds Over New Zealand
- Nacreous Clouds over Sweden
- APOD: 2024 November 19 Á Undulatus Clouds over Las Campanas Observatory
- APOD: 2024 July 7 Á Iridescent Clouds over Sweden
- APOD: 2023 August 20 Á A Roll Cloud Over Wisconsin
- APOD: 2023 February 12 Á Mammatus Clouds over Nebraska