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.

                              2024 February 18
   [2]A nearly perfect circular ring of blue stars is seen against a dark
   field of small background galaxies. In the center of the ring is a ball
        of yellow stars. Please see the explanation for more detailed
                                information.

                 Hoag's Object: A Nearly Perfect Ring Galaxy
   Image Credit: [3]NASA, [4]ESA, [5]Hubble; Processing: [6]Benoit Blanco

   Explanation: Is this one galaxy or two? This question came to light in
   1950 when astronomer [7]Arthur Hoag chanced upon this unusual
   extragalactic object. On the outside is a [8]ring dominated by bright
   blue stars, while near the center lies a ball of much redder stars that
   are likely much older. Between the two is a [9]gap that appears almost
   completely dark. How [10]Hoag's Object formed, including its nearly
   [11]perfectly round ring of stars and gas, remains unknown. Genesis
   hypotheses include a [12]galaxy collision billions of years ago and the
   gravitational effect of a [13]central bar that has [14]since vanished.
   The [15]featured photo was taken by the [16]Hubble Space Telescope and
   reprocessed using an [17]artificially intelligent de-noising algorithm.
   Observations in [18]radio waves indicate that [19]Hoag's Object has not
   accreted a smaller galaxy in the past billion years. [20]Hoag's Object
   spans about 100,000 [21]light years and lies about 600 million
   [22]light years away toward the [23]constellation of the Snake
   ([24]Serpens). Many galaxies far in the distance are visible toward the
   right, while [25]coincidentally, visible in the gap at about seven
   o'clock, is another but more distant [26]ring galaxy.

                      Tomorrow's picture: sideways sun
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    Authors & editors: [38]Robert Nemiroff ([39]MTU) & [40]Jerry Bonnell
                                 ([41]UMCP)
          NASA Official: Amber Straughn; [42]Specific rights apply.
              [43]NASA Web Privacy Policy and Important Notices
                A service of: [44]ASD at [45]NASA / [46]GSFC,
                         [47]NASA Science Activation
                           & [48]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2402/Hoag_HubbleBlanco_3000.jpg
   3. https://www.nasa.gov/
   4. http://www.esa.int/
   5. https://www.nasa.gov/mission_pages/hubble/main/index.html
   6. https://www.astrobin.com/users/Ben_Allen/
   7. https://en.wikipedia.org/wiki/Arthur_Allen_Hoag
   8. https://apod.nasa.gov/apod/ap051022.html
   9. https://apod.nasa.gov/apod/ap040702.html
  10. https://ui.adsabs.harvard.edu/abs/1990ApJ...348..448W/abstract
  11. https://youtu.be/LvpCX89lHvU
  12. https://nedwww.ipac.caltech.edu/level5/Struck/frames.html
  13. https://apod.nasa.gov/apod/ap080622.html
  14. https://ui.adsabs.harvard.edu/abs/2010CeMDA.108...23F/
  15. https://www.astrobin.com/skeebg/D/?nc=user
  16. https://apod.nasa.gov/apod/ap010806.html
  17. https://en.wikipedia.org/wiki/Deep_Image_Prior
  18. https://science.nasa.gov/ems/05_radiowaves
  19. https://ui.adsabs.harvard.edu/abs/2013MNRAS.435..475B/
  20. https://en.wikipedia.org/wiki/Hoag's_Object
  21. https://chandra.harvard.edu/photo/cosmic_distance.html
  22. https://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html
  23. https://spaceplace.nasa.gov/constellations/
  24. https://en.wikipedia.org/wiki/Serpens_(constellation)
  25. https://i.huffpost.com/gadgets/slideshows/252026/slide_252026_1551499_free.jpg
  26. https://apod.nasa.gov/apod/ap150419.html
  27. https://apod.nasa.gov/apod/ap240217.html
  28. https://apod.nasa.gov/apod/archivepix.html
  29. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  30. https://apod.nasa.gov/apod/lib/aptree.html
  31. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  32. https://apod.nasa.gov/apod/calendar/allyears.html
  33. https://apod.com/feed.rss
  34. https://apod.nasa.gov/apod/lib/edlinks.html
  35. https://apod.nasa.gov/apod/lib/about_apod.html
  36. https://asterisk.apod.com/discuss_apod.php?date=240218
  37. https://apod.nasa.gov/apod/ap240219.html
  38. http://www.phy.mtu.edu/faculty/Nemiroff.html
  39. http://www.phy.mtu.edu/
  40. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  41. http://www.astro.umd.edu/
  42. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  43. https://www.nasa.gov/about/highlights/HP_Privacy.html
  44. https://astrophysics.gsfc.nasa.gov/
  45. https://www.nasa.gov/
  46. https://www.nasa.gov/centers/goddard/
  47. https://science.nasa.gov/learners
  48. http://www.mtu.edu/