                        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.

                              2025 December 30
     A star filled sky shows bands of green and purple sky glow. In the
        foreground is a grassy field with clouds on the horizon. Most
     remarkably, a series of short streaks appear like a comet's tail up
   from the horizon toward the upper left. Please see the explanation for
                         more detailed information.

                             An Artificial Comet
                     Image Credit & Copyright: Wang Chao

   Explanation: Yes, but can your comet tail do this? No, and what you are
   seeing is not the tail of a comet. The picture features a cleverly
   overlayed time-lapse sequence of a group of satellites orbiting Earth
   together in June. Specifically, these are Starlink communications
   satellites in low Earth orbit reflecting back sunlight before sunrise
   to Inner Mongolia, China. Although the satellites appear to the human
   eye as points, the 20-second-long camera exposures caused them to
   appear as short streaks. Currently there are over 9000 Starlinks in
   orbit, with more being launched nearly every week. Other satellite
   constellations are also being planned.

                 Explore the Universe: Random APOD Generator
                   Tomorrow's picture: celestial waterfall
     __________________________________________________________________

       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn Specific rights apply.
                  NASA Web Privacy, Accessibility, Notices;
                      A service of: ASD at NASA / GSFC,
                           NASA Science Activation
                             & Michigan Tech. U.

