                        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 January 31

                        The Variable Nebula NGC 2261
     Image Credit & Copyright: Tommy Lease (Denver Astronomical Society)

   Explanation: The interstellar cloud of dust and gas captured in this
   sharp telescopic snapshot is seen to change its appearance noticeably
   over periods as short as a few weeks. Discovered over 200 years ago and
   cataloged as NGC 2261, bright star R Monocerotis lies at the tip of the
   fan-shaped nebula. About one light-year across and 2500 light-years
   away, NGC 2261 was studied early last century by astronomer Edwin
   Hubble and the mysterious cosmic cloud is now more famous as Hubble's
   Variable Nebula. So what makes Hubble's nebula vary? NGC 2261 is
   composed of a dusty reflection nebula fanning out from the star R
   Monocerotis. The leading variability explanation holds that dense knots
   of obscuring dust pass close to R Mon and cast moving shadows across
   the dust clouds in the rest of Hubble's Variable Nebula.

                      Tomorrow's picture: light-weekend
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn Specific rights apply.
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