                        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

                      A Glowing STEVE and the Milky Way
                     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.

                      Tomorrow's picture: doubled stars
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                             & Michigan Tech. U.

