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 April 10 [2]See Explanation. Clicking on the picture will download the highest resolution version available. 38 Hours with the M81 Group Image Credit & [3]Copyright: [4]Daniel Yang K. Explanation: From a garden on planet Earth, 38 hours of exposure with a camera and small telescope produced [5]this cosmic photo of the M81 galaxy group. In fact, the group's dominant galaxy M81 is near the center of the frame sporting grand spiral arms and a bright yellow core. Also known as Bode's galaxy, M81 itself spans some 100,000 light-years. Near the top is cigar-shaped [6]irregular galaxy M82. The pair have been locked in gravitational combat for a billion years. [7]Gravity from each galaxy has profoundly affected the other during a series of cosmic close encounters. Their last go-round lasted about 100 million years and likely raised density waves rippling around M81, resulting in massive star forming regions arrayed along [8]M81's spiral arms. [9]M82 was left with violent star forming regions too, and colliding gas clouds so energetic that the galaxy [10]glows in X-rays. In the next few billion years, their continuing gravitational encounters will result in a merger, and a [11]single galaxy will remain. Another group member, NGC 3077 is below and left of the large spiral M81. Far far away, about 12 million light-years distant the M81 group galaxies are seen toward the northern constellation Ursa Major (the Great Bear). But in the closer foreground the wide-field image is filled with integrated flux nebulae whose faint, [12]dusty interstellar clouds reflect starlight above the plane of our own Milky Way galaxy. Tomorrow's picture: a matinee __________________________________________________________________ [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: Amber Straughn [28]Specific rights apply. [29]NASA Web Privacy Policy and Important Notices A service of: [30]ASD at [31]NASA / [32]GSFC, [33]NASA Science Activation & [34]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2504/38h_M81-group_Jpeg.jpeg 3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 4. https://app.astrobin.com/u/Daniel_Yang_K.#gallery 5. https://app.astrobin.com/u/Daniel_Yang_K.?i=ldzdz7#gallery 6. https://apod.nasa.gov/apod/ap190723.html 7. https://phys.org/news/2019-11-astronomers-stellar-halo.html 8. https://apod.nasa.gov/apod/ap250327.html 9. https://hubblesite.org/contents/news-releases/2001/news-2001-08.html 10. https://chandra.harvard.edu/photo/2006/m82/ 11. https://science.nasa.gov/asset/hubble/collision-scenario-for-milky-way-and-andromeda-galaxy-encounter/ 12. https://apod.nasa.gov/apod/ap160428.html 13. https://apod.nasa.gov/apod/ap250409.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=250410 23. https://apod.nasa.gov/apod/ap250411.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. https://science.nasa.gov/learners 34. http://www.mtu.edu/