Subj : Daily APOD Report
To   : All
From : Alan Ianson
Date : Mon Apr 22 2024 00:09:34

                        Astronomy Picture of the Day

    Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                                2024 April 22
   A dark mountain ridge is pictured across the foreground at the bottom.
    Smoke is rising about the ridge, and a close inspection reveals that
   some of this smoke form rings. The background has a reddish hue, and a
   crescent Moon is visible on the upper left. Please see the explanation
                       for more detailed information.

                     Moon and Smoke Rings from Mt. Etna
                 Image 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.

                          Tomorrow's picture: sky X
     __________________________________________________________________

       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn Specific rights apply.
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                           NASA Science Activation
                             & Michigan Tech. U.

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