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.

                              2019 December 16

                  The Magnetic Fields of Spiral Galaxy M77
      Image Credit: NASA, SOFIA, HAWC+; JPL-Caltech, Roma Tre. U.; ESA,
                            Hubble, NuSTAR, SDSS

   Explanation: Can magnetic fields help tell us how spiral galaxies form
   and evolve? To find out, the HAWC+ instrument on NASA's airborne (747)
   SOFIA observatory observed nearby spiral galaxy M77. HAWC+ maps
   magnetism by observing polarized infrared light emitted by elongated
   dust grains rotating in alignment with the local magnetic field. The
   HAWC+ image shows that magnetic fields do appear to trace the spiral
   arms in the inner regions of M77, arms that likely highlight density
   waves in the inflowing gas, dust and stars caused by the gravity of the
   galaxy's oval shape. The featured picture superposes the HAWC+ image
   over diffuse X-ray emission mapped by NASA's NuSTAR satellite and
   visible light images taken by Hubble and the SDSS. M77 is located about
   47 million light years away toward the constellation of the Sea Monster
   (Cetus).

                      Tomorrow's picture: red and dusty
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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.

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