Astronomy Picture of the Day

   [1]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.

                                2025 July 22
     [2]A nearly circular nebula with two rings is shown. The outer ring
   appears orange while while the inner rings is more complex and appears
       blue. Please see the explanation for more detailed information.

                        A Double Detonation Supernova
          Image Credit: [3]ESO, [4]P. Das et al.; Background stars
                     ([5]NASA/[6]Hubble): K. Noll et al.

   Explanation: Can some supernovas explode twice? Yes, when the first
   explosion acts like a [7]detonator for the second. This is a leading
   hypothesis for the cause of supernova remnant (SNR) [8]0509-67.5. In
   this [9]two-star system, gravity causes the larger and fluffier star to
   [10]give up mass to a smaller and denser [11]white dwarf companion.
   Eventually the [12]white dwarf's near-surface temperature goes so high
   that it explodes, creating a shock wave that goes [13]both out and in
   -- and so triggers a full [14]Type Ia supernova near the center. Recent
   images of the SNR 0509-67.5 system, like the [15]featured image from
   the [16]Very Large Telescope in [17]Chile, show two shells with radii
   and compositions consistent with the [18]double detonation hypothesis.
   This system, [19]SNR 0509-67.5 is also famous for [20]two standing
   mysteries: why its [21]bright supernova wasn't noted 400 years ago, and
   [22]why no visible companion star remains.

                  Tomorrow's picture: rock being vaporized
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    Authors & editors: [34]Robert Nemiroff ([35]MTU) & [36]Jerry Bonnell
                                 ([37]UMCP)
          NASA Official: Amber Straughn [38]Specific rights apply.
            [39]NASA Web Privacy, [40]Accessibility, [41]Notices;
                A service of: [42]ASD at [43]NASA / [44]GSFC,
                         [45]NASA Science Activation
                           & [46]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2507/DoubleSN_ESO_3000.jpg
   3. https://www.eso.org/
   4. https://www.unsw.edu.au/hdr/priyam-das
   5. https://www.nasa.gov/
   6. https://science.nasa.gov/mission/hubble/
   7. https://en.wikipedia.org/wiki/Detonator
   8. https://www.eso.org/public/videos/eso2511b/
   9. https://apod.nasa.gov/apod/ap970219.html
  10. https://en.wikipedia.org/wiki/Roche_lobe
  11. https://science.nasa.gov/universe/stars/types/#white-dwarfs
  12. https://apod.nasa.gov/apod/ap950910.html
  13. https://www.eso.org/public/videos/eso2511c/
  14. https://en.wikipedia.org/wiki/Type_Ia_supernova
  15. https://www.eso.org/public/images/eso2511a/
  16. https://www.eso.org/public/teles-instr/paranal-observatory/vlt/
  17. https://en.wikipedia.org/wiki/Chile
  18. https://ui.adsabs.harvard.edu/abs/2025NatAs.tmp..135D/abstract
  19. https://en.wikipedia.org/wiki/SNR_0509-67.5
  20. https://www.shutterstock.com/image-photo/funny-duo-two-black-white-600nw-1209024034.jpg
  21. https://apod.nasa.gov/apod/ap110125.html
  22. https://apod.nasa.gov/apod/ap120112.html
  23. https://apod.nasa.gov/apod/ap250721.html
  24. https://apod.nasa.gov/apod/archivepix.html
  25. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  26. https://apod.nasa.gov/apod/lib/aptree.html
  27. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  28. https://apod.nasa.gov/apod/calendar/allyears.html
  29. https://apod.com/feed.rss
  30. https://apod.nasa.gov/apod/lib/edlinks.html
  31. https://apod.nasa.gov/apod/lib/about_apod.html
  32. https://asterisk.apod.com/discuss_apod.php?date=250722
  33. https://apod.nasa.gov/apod/ap250723.html
  34. http://www.phy.mtu.edu/faculty/Nemiroff.html
  35. http://www.phy.mtu.edu/
  36. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  37. http://www.astro.umd.edu/
  38. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  39. https://www.nasa.gov/about/highlights/HP_Privacy.html
  40. https://www.nasa.gov/general/accessibility/
  41. https://www.nasa.gov/privacy/
  42. https://astrophysics.gsfc.nasa.gov/
  43. https://www.nasa.gov/
  44. https://www.nasa.gov/centers/goddard/
  45. https://science.nasa.gov/learners
  46. http://www.mtu.edu/