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.

                              2026 September 18
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                      Messier 33: The Triangulum Galaxy
            Image Credit & [3]Copyright: [4]George Chatzifrantzis

   Explanation: The small, northern constellation [5]Triangulum harbors
   this magnificent face-on spiral galaxy, Messier 33. Its popular names
   include the Pinwheel Galaxy or just the [6]Triangulum Galaxy. M33 is
   over 50,000 light-years in diameter, third largest in the [7]Local
   Group of galaxies after the Andromeda Galaxy (M31), and our own Milky
   Way. [8]About 3 million light-years from the Milky Way, M33 is itself
   thought to be a satellite of the Andromeda Galaxy and [9]astronomers in
   these two galaxies would likely have spectacular views of each other's
   grand spiral star systems. As for the view from the Milky Way, this
   [10]sharp telescopic image shows off M33's blue star clusters and
   pinkish [11]star forming regions along the galaxy's loosely wound
   spiral arms. In fact, the [12]cavernous NGC 604 is the brightest star
   forming region, seen here at about the 5 o'clock position from the
   galaxy center. Like M31, M33's population of well-measured variable
   stars have helped make this nearby spiral a cosmic yardstick for
   [13]establishing the distance [14]scale of the Universe.

       APOD's main NASA site is [15]moving: From [16]apod.nasa.gov to
                          [17]science.nasa.gov/apod
                   Tomorrow's picture: star party weekend
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      Authors & editors: [29]Robert Nemiroff ([30]MTU) & Jerry Bonnell
                                 ([31]UMCP)
          NASA Official: Amber Straughn [32]Specific rights apply.
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                A service of: [36]ASD at [37]NASA / [38]GSFC,
                         [39]NASA Science Activation
                           & [40]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2609/m33m14_rasa3NM.jpg
   3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
   4. https://www.facebook.com/GeorgeChatzifrantzis/
   5. http://www.hawastsoc.org/deepsky/tri/index.html
   6. https://science.nasa.gov/mission/hubble/science/explore-the-night-sky/hubble-messier-catalog/messier-33/
   7. https://en.wikipedia.org/wiki/Local_Group
   8. https://apod.nasa.gov/apod/ap211106.html
   9. https://arxiv.org/abs/astro-ph?papernum=0506609
  10. https://www.facebook.com/photo?fbid=29170483172553330&set=a.627529503942078
  11. https://apod.nasa.gov/apod/ap091017.html
  12. https://science.nasa.gov/image-detail/9697_full_jpg/
  13. https://adsabs.harvard.edu/cgi-bin/bib_query?1926ApJ....63..236H
  14. https://antwrp.gsfc.nasa.gov/diamond_jubilee/debate96.html
  15. https://asterisk.apod.com/viewtopic.php?t=45023
  16. https://apod.nasa.gov/
  17. https://science.nasa.gov/apod
  18. https://apod.nasa.gov/apod/ap260917.html
  19. https://apod.nasa.gov/apod/archivepix.html
  20. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  21. https://apod.nasa.gov/apod/lib/aptree.html
  22. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  23. https://apod.nasa.gov/apod/calendar/allyears.html
  24. https://apod.com/feed.rss
  25. https://apod.nasa.gov/apod/lib/edlinks.html
  26. https://apod.nasa.gov/apod/lib/about_apod.html
  27. https://asterisk.apod.com/discuss_apod.php?date=260918
  28. https://apod.nasa.gov/apod/ap260919.html
  29. https://www.mtu.edu/physics/department/faculty/nemiroff/
  30. https://www.mtu.edu/physics
  31. https://www.astro.umd.edu/
  32. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  33. https://www.nasa.gov/about/highlights/HP_Privacy.html
  34. https://www.nasa.gov/general/accessibility/
  35. https://www.nasa.gov/privacy/
  36. https://astrophysics.gsfc.nasa.gov/
  37. https://www.nasa.gov/
  38. https://www.nasa.gov/centers/goddard/
  39. https://science.nasa.gov/learners
  40. http://www.mtu.edu/