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. 2025 January 30 [2]See Explanation. Clicking on the picture will download the highest resolution version available. Hydrogen Clouds of M33 Image Credit & [3]Copyright: [4]Pea Mauro 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 60,000 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 filter that transmits the light of the strongest visible hydrogen and oxygen [9]emission lines. Tomorrow's picture: pixels in space __________________________________________________________________ [10]< | [11]Archive | [12]Submissions | [13]Index | [14]Search | [15]Calendar | [16]RSS | [17]Education | [18]About APOD | [19]Discuss | [20]> __________________________________________________________________ Authors & editors: [21]Robert Nemiroff ([22]MTU) & [23]Jerry Bonnell ([24]UMCP) NASA Official: Amber Straughn [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/2501/M33_2048.jpg 3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 4. https://www.astrobin.com/users/Pea@Mauro/ 5. https://apod.nasa.gov/apod/ap211106.html 6. https://www.astrobin.com/vvx0t5/ 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/ap250129.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=250130 20. https://apod.nasa.gov/apod/ap250131.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/