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 October 28
A night sky is shown with a bright red band running
overhead. Above the red band is a diffuse red glow.
A path through a grassy filed is in the foreground
with a path going out toward the horizon. 
Please see the explanation for more detailed information.

STEVE: A Glowing River over France
Credit & Copyright: Louis LEROUX-GÉRÉ

Explanation: Sometimes a river of hot gas flows over your head. In this case the river created a Strong Thermal Emission Velocity Enhancement (STEVE) that glowed bright red, white, and pink. Details of how STEVEs work remain a topic of research, but recent evidence holds that their glow results from a fast-moving river of hot ions flowing over a hundred kilometers up in the Earth's atmosphere: the ionosphere. The more expansive dull red glow might be related to the flowing STEVE, but alternatively might be a Stable Auroral Red (SAR) arc, a more general heat-related glow. The featured picture, taken earlier this month in Côte d'Opale, France, is a wide-angle digital composite made as the STEVE arc formed nearly overhead. Although the apparition lasted only a few minutes, this was long enough for the quick-thinking astrophotographer to get in the picture -- can you find him?

Tomorrow's picture: webb stars


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