Monday, April 22, 2024

APOD - Moon and Smoke Rings from Mt. Etna

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


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