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Астронет: Астрономическая картинка дня Луна и кольца из дыма над горой Этна http://variable-stars.ru/db/msg/1927311/eng |
Credit & Copyright: Dario Giannobile
Explanation:
Yes, but can your volcano do this?
To the
surprise of some,
Mt. Etna emits,
on occasion, smoke rings.
Technically known as
vortex rings,
the walls of the volcano slightly slow the outside of
emitted smoke puffs,
causing the inside gas to move faster.
A circle of low pressure develops so that the emitted puff of
volcanic gas and
ash
loops around in a
ring,
a familiar geometric structure that can be surprisingly stable as it rises.
Smoke rings
are quite rare and need a coincidence of the right
geometry
of the vent, the right speed of
ejected smoke,
and the relative calmness of the outside atmosphere.
In the
featured image taken about two weeks ago from
Gangi,
Sicily,
Italy,
multiple volcanic smoke rings are visible.
The scene is shaded by the
red light of a dawn
Sun, while a
crescent Moon
is visible in the background.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.