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 __________________________________________________________________ [13]< | [14]Archive | [15]Submissions | [16]Index | [17]Search | [18]Calendar | [19]RSS | [20]Education | [21]About APOD | [22]Discuss | [23]> __________________________________________________________________ Authors & editors: [24]Robert Nemiroff ([25]MTU) & [26]Jerry Bonnell ([27]UMCP) NASA Official: Phillip Newman [28]Specific rights apply. [29]NASA Web Privacy Policy and Important Notices 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/