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 19

                               Orion in Depth
               Illustration Credit & Copyright: Ronald Davison

   Explanation: Orion is a familiar constellation. The apparent positions
   of its stars in two dimensions create a well-known pattern on the bowl
   of planet Earth's night sky. Orion may not look quite so familiar in
   this 3D view though. The illustration reconstructs the relative
   positions of Orion's bright stars, including data from the Hipparcus
   catalog of parallax distances. The most distant star shown is Alnilam.
   The middle one in the projected line of three that make up Orion's belt
   when viewed from planet Earth, Alnilam is nearly 2,000 light-years
   away, almost 3 times as far as fellow belt stars Alnitak and Mintaka.
   Though Rigel and Betelgeuse apparently shine brighter in planet Earth's
   sky, that makes more distant Alnilam intrinsically (in absolute
   magnitude) the brightest of the familiar stars in Orion. In the
   Hipparcus catalog, errors in measured parallaxes for Orion's stars can
   translate in to distance errors of a 100 light-years or so.

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