                        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.

                              2020 September 3

                            A Halo for Andromeda
    Digital Illustration Credit: NASA, ESA, J. DePasquale and E. Wheatley
                            (STScI) and Z. Levay

   Explanation: M31, the Andromeda Galaxy, is the closest large spiral
   galaxy to our Milky Way. Some 2.5 million light-years distant it shines
   in Earth's night sky as a small, faint, elongated cloud just visible to
   the unaided eye. Invisible to the eye though, its enormous halo of hot
   ionized gas is represented in purplish hues for this digital
   illustration of our neighboring galaxy above rocky terrain. Mapped by
   Hubble Space Telescope observations of the absorption of ultraviolet
   light against distant quasars, the extent and make-up of Andromeda's
   gaseous halo has been recently determined by the AMIGA project. A
   reservoir of material for future star formation, Andromeda's halo of
   diffuse plasma was measured to extend around 1.3 million light-years or
   more from the galaxy. That's about half way to the Milky Way, likely
   putting it in contact with the diffuse gaseous halo of our own galaxy.

                     Tomorrow's picture: pixels in space
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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