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.

                               2023 October 13
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                           Hydrogen Clouds of M33
              Image Credit & [3]Copyright: [4]Reinhold Wittich

   Explanation: Gorgeous spiral galaxy Messier 33 seems to have more than
   its fair share of glowing hydrogen gas. A prominent member of the local
   group of galaxies, M33 is also known as the [5]Triangulum Galaxy and
   lies a mere 3 million light-years away. The galaxy's central 30,000
   light-years or so are shown in this [6]sharp galaxy portrait. The
   portrait features M33's reddish ionized hydrogen clouds or [7]HII
   regions. Sprawling along loose spiral arms that wind toward the core,
   [8]M33's giant HII regions are some of the largest known stellar
   nurseries, sites of the formation of short-lived but very massive
   stars. Intense ultraviolet radiation from the luminous, massive stars
   ionizes the surrounding hydrogen gas and ultimately produces the
   characteristic red glow. In this image, broadband data were combined
   with narrowband data recorded through a hydrogen-alpha filter. That
   filter transmits the light of the strongest visible hydrogen
   [9]emission line.

                   Tomorrow's picture: ring around the Sun
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    Authors & editors: [21]Robert Nemiroff ([22]MTU) & [23]Jerry Bonnell
                                 ([24]UMCP)
          NASA Official: Phillip Newman [25]Specific rights apply.
              [26]NASA Web Privacy Policy and Important Notices
                A service of: [27]ASD at [28]NASA / [29]GSFC,
                         [30]NASA Science Activation
                           & [31]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2310/M33_Triangulum.jpg
   3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
   4. https://www.wittich.com/
   5. https://apod.nasa.gov/apod/ap211106.html
   6. https://www.wittich.com/?p=9882
   7. http://en.wikipedia.org/wiki/H_II_region
   8. https://hubblesite.org/contents/media/images/2003/30/1422-Image.html
   9. https://webbtelescope.org/contents/articles/spectroscopy-101--how-absorption-and-emission-spectra-work
  10. https://apod.nasa.gov/apod/ap231012.html
  11. https://apod.nasa.gov/apod/archivepix.html
  12. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  13. https://apod.nasa.gov/apod/lib/aptree.html
  14. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  15. https://apod.nasa.gov/apod/calendar/allyears.html
  16. https://apod.nasa.gov/apod.rss
  17. https://apod.nasa.gov/apod/lib/edlinks.html
  18. https://apod.nasa.gov/apod/lib/about_apod.html
  19. http://asterisk.apod.com/discuss_apod.php?date=231013
  20. https://apod.nasa.gov/apod/ap231014.html
  21. http://www.phy.mtu.edu/faculty/Nemiroff.html
  22. http://www.phy.mtu.edu/
  23. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  24. http://www.astro.umd.edu/
  25. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  26. https://www.nasa.gov/about/highlights/HP_Privacy.html
  27. https://astrophysics.gsfc.nasa.gov/
  28. https://www.nasa.gov/
  29. https://www.nasa.gov/centers/goddard/
  30. https://science.nasa.gov/learners
  31. http://www.mtu.edu/