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 July 8
      [2]A cluster of bright blue stars is seen near the bottom of this
      starfield. Nebula around the stars is blue near the stars but red
    elsewhere. Please see the explanation for more detailed information.

                        The Pleiades in Red and Blue
   Image Credit & Copyright: [3]Ogetay Kayali ([4]Michigan Tech U.) Text:
                   [5]Ogetay Kayali ([6]Michigan Tech U.)

   Explanation: If you have looked at the sky and seen a group of stars
   about the size of the full Moon, that's the [7]Pleiades (M45). Perhaps
   the most famous [8]star cluster in the sky, its brightest stars can be
   seen even from the [9]light-polluted cities. But your unaided eye can
   also see its nebulosity -- the gas and dust surrounding it -- [10]under
   dark skies. However, telescopes can catch even more. The bright blue
   stars of the Pleiades, also known as the [11]Seven Sisters, light up
   their surrounding dust, causing it to appear a diffuse blue that can
   only be seen under long exposures. But that's not all. The [12]cosmic
   dust appears to stretch upward like [13]ethereal arms. And the entire
   structure is surrounded by a [14]reddish glow from the most abundant
   [15]element in the universe: hydrogen. The [16]featured image is
   composed of nearly 25 hours of exposure and was captured last year from
   [17]Starfront Observatory, in [18]Texas, [19]USA

              Explore Your Universe: [20]Random APOD Generator
                       Tomorrow's picture: open space
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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/2507/Pleiades_Kayali_2560.jpg
   3. https://www.ogetay.com/
   4. https://www.mtu.edu/physics/
   5. https://www.ogetay.com/
   6. https://www.mtu.edu/physics/
   7. https://apod.nasa.gov/apod/ap241209.html
   8. https://science.nasa.gov/universe/star-clusters-inside-the-universes-stellar-collections/
   9. https://apod.nasa.gov/apod/ap200408.html
  10. https://apod.nasa.gov/apod/ap230308.html
  11. https://en.wikipedia.org/wiki/Pleiades#Origin_of_name
  12. https://herscheltelescope.org.uk/science/infrared/dust/
  13. https://www.reddit.com/media?url=https://preview.redd.it/our-cat-lies-like-this-on-us-with-her-arms-stretched-out-v0-b7rxaush7vub1.jpeg?width=4032&format=pjpg&auto=webp&s=5cfd7f613fb481e89a980efa704e7fca9382f83a
  14. https://en.wikipedia.org/wiki/Hydrogen-alpha
  15. https://apod.nasa.gov/apod/ap230108.html
  16. https://www.astrobin.com/zcwwdj/
  17. https://starfront.space/
  18. https://en.wikipedia.org/wiki/Texas
  19. https://en.wikipedia.org/wiki/United_States
  20. https://apod.nasa.gov/apod/random_apod.html
  21. https://apod.nasa.gov/apod/ap250707.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=250708
  31. https://apod.nasa.gov/apod/ap250709.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/