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 February 26
   [2]A cluster of galaxies is shown with many galaxies around the cluster
    center. A close look at this center shows that it is encompassed by a
     narrow ring of light. Please see the explanation for more detailed
                                information.

                Einstein Ring Surrounds Nearby Galaxy Center
      Image Credit & Copyright: [3]ESA, [4]NASA, [5]Euclid Consortium;
             Processing: [6]J.-C. Cuillandre, G. Anselmi, T. Li

   Explanation: Do you see the ring? If you look very closely at the
   center of the featured galaxy [7]NGC 6505, a ring becomes evident. It
   is the gravity of [8]NGC 6505, the nearby ([9]z = 0.042) [10]elliptical
   galaxy that you can easily see, that is [11]magnifying and distorting
   the image of a [12]distant galaxy into a complete circle. To create a
   complete [13]Einstein ring there must be perfect alignment of the
   nearby galaxy's center and part of the background galaxy. [14]Analysis
   of this ring and the multiple images of the background galaxy help to
   determine the mass and fraction of [15]dark matter in NGC 6505's
   center, as well as uncover previously [16]unseen details in the
   distorted galaxy. The [17]featured image was captured by [18]ESA's
   Earth-orbiting [19]Euclid telescope in 2023 and released earlier this
   month.

                       Tomorrow's picture: open space
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    Authors & editors: [31]Robert Nemiroff ([32]MTU) & [33]Jerry Bonnell
                                 ([34]UMCP)
          NASA Official: Amber Straughn [35]Specific rights apply.
            [36]NASA Web Privacy, [37]Accessibility, [38]Notices;
                A service of: [39]ASD at [40]NASA / [41]GSFC,
                         [42]NASA Science Activation
                           & [43]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2502/ClusterRing_Euclid_2665.jpg
   3. https://www.esa.int/
   4. https://www.nasa.gov/
   5. https://www.euclid-ec.org/consortium/about-ec/
   6. https://www.cfht.hawaii.edu/~jcc/
   7. https://en.wikipedia.org/wiki/NGC_6505
   8. https://www.euclid-ec.org/einstein-ring-in-ngc-6505/
   9. https://science.nasa.gov/mission/hubble/science/science-behind-the-discoveries/hubble-cosmological-redshift/
  10. https://en.wikipedia.org/wiki/Elliptical_galaxy
  11. https://www.reddit.com/r/photoshopbattles/comments/spff2s/psbattle_this_dog_staring_at_the_camera/#lightbox
  12. https://apod.nasa.gov/apod/ap210802.html
  13. https://apod.nasa.gov/apod/ap111221.html
  14. https://arxiv.org/abs/2502.06505
  15. https://science.nasa.gov/universe/dark-matter-dark-energy/
  16. https://apod.nasa.gov/apod/ap220705.html
  17. https://www.jpl.nasa.gov/news/euclid-discovers-einstein-ring-in-our-cosmic-backyard/
  18. https://www.esa.int/
  19. https://www.esa.int/Science_Exploration/Space_Science/Euclid_overview
  20. https://apod.nasa.gov/apod/ap250225.html
  21. https://apod.nasa.gov/apod/archivepix.html
  22. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  23. https://apod.nasa.gov/apod/lib/aptree.html
  24. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  25. https://apod.nasa.gov/apod/calendar/allyears.html
  26. https://apod.com/feed.rss
  27. https://apod.nasa.gov/apod/lib/edlinks.html
  28. https://apod.nasa.gov/apod/lib/about_apod.html
  29. https://asterisk.apod.com/discuss_apod.php?date=250226
  30. https://apod.nasa.gov/apod/ap250227.html
  31. http://www.phy.mtu.edu/faculty/Nemiroff.html
  32. http://www.phy.mtu.edu/
  33. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  34. http://www.astro.umd.edu/
  35. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  36. https://www.nasa.gov/about/highlights/HP_Privacy.html
  37. https://www.nasa.gov/general/accessibility/
  38. https://www.nasa.gov/privacy/
  39. https://astrophysics.gsfc.nasa.gov/
  40. https://www.nasa.gov/
  41. https://www.nasa.gov/centers/goddard/
  42. https://science.nasa.gov/learners
  43. http://www.mtu.edu/