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.
2020 November 17
Image Credit: NASA, Krista Trinder
Explanation: What's creating these long glowing streaks in the sky? No one is sure. Known as Strong Thermal Emission Velocity Enhancements (STEVEs), these luminous light-purple sky ribbons may resemble regular auroras, but recent research reveals significant differences. A STEVE's great length and unusual colors, when measured precisely, indicate that it may be related to a subauroral ion drift (SAID), a supersonic river of hot atmospheric ions thought previously to be invisible. Some STEVEs are now also thought to be accompanied by green picket fence structures, a series of sky slats that can appear outside of the main auroral oval that does not involve much glowing nitrogen. The featured wide-angle composite image shows a STEVE in a dark sky above Childs Lake, Manitoba, Canada in 2017, crossing in front of the central band of our Milky Way Galaxy.
Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
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