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 November 16

                        The Star Streams of NGC 5907
      Image Credit & Copyright: R Jay Gabany (Blackbird Observatory) -
                collaboration; D.Martinez-Delgado(IAC, MPIA),
    J.Penarrubia (U.Victoria) I. Trujillo (IAC) S.Majewski (U.Virginia),
                             M.Pohlen (Cardiff)

   Explanation: Grand tidal streams of stars seem to surround galaxy NGC
   5907. The arcing structures form tenuous loops extending more than
   150,000 light-years from the narrow, edge-on spiral, also known as the
   Splinter or Knife Edge Galaxy. Recorded only in very deep exposures,
   the streams likely represent the ghostly trail of a dwarf galaxy -
   debris left along the orbit of a smaller satellite galaxy that was
   gradually torn apart and merged with NGC 5907 over four billion years
   ago. Ultimately this remarkable discovery image, from a small robotic
   observatory in New Mexico, supports the cosmological scenario in which
   large spiral galaxies, including our own Milky Way, were formed by the
   accretion of smaller ones. NGC 5907 lies about 40 million light-years
   distant in the northern constellation Draco.

                    Tomorrow's picture: WISE young stars
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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