                        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.

                               2024 February 9

                            When Roses Aren't Red
     Image Credit & Copyright: Tommy Lease (Denver Astronomical Society)

   Explanation: Not all roses are red of course, but they can still be
   very pretty. Likewise, the beautiful Rosette Nebula and other star
   forming regions are often shown in astronomical images with a
   predominately red hue, in part because the dominant emission in the
   nebula is from hydrogen atoms. Hydrogen's strongest optical emission
   line, known as H-alpha, is in the red region of the spectrum. But the
   beauty of an emission nebula need not be appreciated in red light
   alone. Other atoms in the nebula are also excited by energetic
   starlight and produce narrow emission lines as well. In this close-up
   view of the Rosette Nebula, narrowband images are mapped into broadband
   colors to show emission from Sulfur atoms in red, Hydrogen in green,
   and Oxygen in blue. In fact, the scheme of mapping these narrow atomic
   emission lines (SHO) into the broader colors (RGB) is adopted in many
   Hubble images of emission nebulae. This image spans about 50
   light-years across the center of the Rosette Nebula. The nebula lies
   some 3,000 light-years away in the constellation Monoceros.

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