                        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.

                                 2026 May 16

                         Aurora Slathers Up the Sky
               Image Credit: Jack Fischer, Expedition 52, NASA

   Explanation: Like salsa verde on your favorite burrito, a green aurora
   slathers up the sky in this 2017 June 25 snapshot from the
   International Space Station. About 400 kilometers (250 miles) above
   Earth, the orbiting station is itself within the upper realm of the
   auroral displays. Aurorae have the signature colors of excited
   molecules and atoms at the low densities found at extreme altitudes.
   Emission from atomic oxygen dominates this view. The tantalizing glow
   is green at lower altitudes, but rarer reddish bands extend above the
   space station's horizon. The orbital scene was captured while passing
   over a point south and east of Australia, with stars above the horizon
   at the right belonging to the constellation Canis Major, Orion's big
   dog. Sirius, alpha star of Canis Major, is the brightest star near the
   Earth's limb.

                      Tomorrow's picture: spiral barred
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       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.

