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.

                               2019 October 3
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                         The Hydrogen Clouds of M33
   Image Data: [3]Subaru Telescope ([4]NAOJ), [5]Hubble Space Telescope -
                     Image Processing: [6]Robert Gendler
   Additional Data: [7]BYU, Robert Gendler, Johannes Schedler, Adam Block
             - Copyright: Robert Gendler, Subaru Telescope, NAOJ

   Explanation: Gorgeous spiral galaxy M33 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 [8]Triangulum Galaxy and
   lies a mere 3 million light-years away. The galaxy's inner 30,000
   light-years or so are shown in this [9]magnificent 25 panel telescopic
   mosaic. Based on image data from space and ground-based telescopes, the
   portrait of M33 shows off the galaxy's reddish ionized hydrogen clouds
   or [10]HII regions. Sprawling along loose spiral arms that wind toward
   the core, [11]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. To enhance this image, broadband data was used
   to produce a color view of the galaxy and combined with narrowband data
   recorded through a hydrogen-alpha filter. That filter transmits the
   light of the strongest visible hydrogen [12]emission line.

                     Tomorrow's picture: pixels in space
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    Authors & editors: [24]Robert Nemiroff ([25]MTU) & [26]Jerry Bonnell
                                 ([27]UMCP)
          NASA Official: Phillip Newman [28]Specific rights apply.
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                A service of: [30]ASD at [31]NASA / [32]GSFC
                           & [33]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/1910/M33-Subaru-Gendler-LL.jpg
   3. http://www.naoj.org/Introduction/index.html
   4. http://www.naoj.org/
   5. http://hla.stsci.edu/hla_welcome.html
   6. http://www.robgendlerastropics.com/
   7. http://wmo.byu.edu/
   8. https://apod.nasa.gov/apod/ap160917.html
   9. http://www.robgendlerastropics.com/M33-Subaru-Gendler.html
  10. http://en.wikipedia.org/wiki/H_II_region
  11. http://hubblesite.org/newscenter/archive/releases/2003/30/
  12. https://www.khanacademy.org/partner-content/nasa/measuringuniverse/spectroscopy/a/absorptionemission-lines
  13. https://apod.nasa.gov/apod/ap191002.html
  14. https://apod.nasa.gov/apod/archivepix.html
  15. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  16. https://apod.nasa.gov/apod/lib/aptree.html
  17. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  18. https://apod.nasa.gov/apod/calendar/allyears.html
  19. https://apod.nasa.gov/apod.rss
  20. https://apod.nasa.gov/apod/lib/edlinks.html
  21. https://apod.nasa.gov/apod/lib/about_apod.html
  22. http://asterisk.apod.com/discuss_apod.php?date=191003
  23. https://apod.nasa.gov/apod/ap191004.html
  24. http://www.phy.mtu.edu/faculty/Nemiroff.html
  25. http://www.phy.mtu.edu/
  26. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  27. http://www.astro.umd.edu/
  28. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  29. https://www.nasa.gov/about/highlights/HP_Privacy.html
  30. https://astrophysics.gsfc.nasa.gov/
  31. https://www.nasa.gov/
  32. https://www.nasa.gov/centers/goddard/
  33. http://www.mtu.edu/