                        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.

                                2023 March 3

                    RCW 86: Historical Supernova Remnant
        Image Credit: CTIO/NOIRLab/DOE/NSF/AURA, T.A. Rector (Univ.of
                           Alaska/NSF’s NOIRLab),
   J. Miller (Gemini Obs./NSF’s NOIRLab), M. Zamani & D. de Martin (NSF’s
                                  NOIRLab)

   Explanation: In 185 AD, Chinese astronomers recorded the appearance of
   a new star in the Nanmen asterism. That part of the sky is identified
   with Alpha and Beta Centauri on modern star charts. The new star was
   visible to the naked-eye for months, and is now thought to be the
   earliest recorded supernova. This deep telescopic view reveals the
   wispy outlines of emission nebula RCW 86, just visible against the
   starry background, understood to be the remnant of that stellar
   explosion. Captured by the wide-field Dark Energy Camera operating at
   Cerro Tololo Inter-American Observatory in Chile, the image traces the
   full extent of a ragged shell of gas ionized by the still expanding
   shock wave. Space-based images indicate an abundance of the element
   iron in RCW 86 and the absence of a neutron star or pulsar within the
   remnant, suggesting that the original supernova was Type Ia. Unlike the
   core collapse supernova explosion of a massive star, a Type Ia
   supernova is a thermonuclear detonation on a white dwarf star that
   accretes material from a companion in a binary star system. Near the
   plane of our Milky Way galaxy and larger than the full moon on the sky
   this supernova remnant is too faint to be seen by eye though. RCW 86 is
   some 8,000 light-years distant and around 100 light-years across.

              Tomorrow's picture: 10 days of Venus and Jupiter
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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