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 7
    [2]A bright spiral galaxy fills the image with blue spiral arms laced
      with red-brown dust. Please see the explanation for more detailed
                                information.

                    NGC 4414: A Flocculent Spiral Galaxy
      Image Credit: [3]ESA/Hubble & [4]NASA, [5]O. Graur, S. W. Jha, A.
                                 Filippenko

   Explanation: How much mass do flocculent spirals hide? The [6]featured
   image of [7]flocculent spiral galaxy NGC 4414 was taken with the
   [8]Hubble Space Telescope to help answer this question. [9]Flocculent
   spirals -- galaxies without well-defined spiral arms -- are a quite
   common form of galaxy, and [10]NGC 4414 is one of the closest.
   [11]Stars and gas near the visible edge of [12]spiral galaxies orbit
   the center so fast that the gravity from a large amount of unseen
   [13]dark matter must be present to hold them together.
   [14]Understanding the matter and [15]dark matter distribution of NGC
   4414 helps humanity calibrate the rest of the galaxy and, by deduction,
   [16]flocculent spirals in general. Further, calibrating the
   [17]distance to [18]NGC 4414 helps humanity calibrate the cosmological
   distance [19]scale of the entire [20]visible universe.

                      Tomorrow's picture: Moon sisters
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    Authors & editors: [32]Robert Nemiroff ([33]MTU) & [34]Jerry Bonnell
                                 ([35]UMCP)
          NASA Official: Amber Straughn [36]Specific rights apply.
            [37]NASA Web Privacy, [38]Accessibility, [39]Notices;
                A service of: [40]ASD at [41]NASA / [42]GSFC,
                         [43]NASA Science Activation
                           & [44]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2504/Ngc4414B_Hubble_1280.jpg
   3. https://esahubble.org/
   4. https://www.nasa.gov/
   5. https://lweb.cfa.harvard.edu/~orgraur/
   6. https://esahubble.org/images/potw2444a/
   7. https://en.wikipedia.org/wiki/Flocculent_spiral_galaxy
   8. https://apod.nasa.gov/apod/ap010806.html
   9. https://en.wiktionary.org/wiki/flocculent
  10. https://en.wikipedia.org/wiki/NGC_4414
  11. https://apod.nasa.gov/apod/ap130606.html
  12. https://en.wikipedia.org/wiki/Spiral_galaxy
  13. https://www.nasa.gov/audience/forstudents/9-12/features/what-is-dark-matter.html
  14. http://66.media.tumblr.com/tumblr_m5hfctHc7i1rrgr1no1_1280.jpg
  15. https://science.nasa.gov/dark-matter/
  16. https://astronomy.swin.edu.au/cms/astro/cosmos/F/Flocculent+Spiral
  17. https://en.wikipedia.org/wiki/Cosmic_distance_ladder
  18. http://adsabs.harvard.edu/abs/2014A&A...566A..80D
  19. http://antwrp.gsfc.nasa.gov/debate/debate96.html
  20. https://ui.adsabs.harvard.edu/abs/1998ApJ...509...80S/abstract
  21. https://apod.nasa.gov/apod/ap250406.html
  22. https://apod.nasa.gov/apod/archivepix.html
  23. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  24. https://apod.nasa.gov/apod/lib/aptree.html
  25. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  26. https://apod.nasa.gov/apod/calendar/allyears.html
  27. https://apod.com/feed.rss
  28. https://apod.nasa.gov/apod/lib/edlinks.html
  29. https://apod.nasa.gov/apod/lib/about_apod.html
  30. https://asterisk.apod.com/discuss_apod.php?date=250407
  31. https://apod.nasa.gov/apod/ap250408.html
  32. http://www.phy.mtu.edu/faculty/Nemiroff.html
  33. http://www.phy.mtu.edu/
  34. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  35. http://www.astro.umd.edu/
  36. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  37. https://www.nasa.gov/about/highlights/HP_Privacy.html
  38. https://www.nasa.gov/general/accessibility/
  39. https://www.nasa.gov/privacy/
  40. https://astrophysics.gsfc.nasa.gov/
  41. https://www.nasa.gov/
  42. https://www.nasa.gov/centers/goddard/
  43. https://science.nasa.gov/learners
  44. http://www.mtu.edu/