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 4
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                              Hickson 44 in Leo
                  Image Credit & [3]Copyright: [4]Jiang Wu

   Explanation: Scanning the skies for galaxies, Canadian astronomer Paul
   Hickson and colleagues identified some 100 compact [5]groups of
   galaxies, now appropriately called [6]Hickson Compact Groups. The four
   prominent galaxies seen in this intriguing [7]telescopic skyscape are
   one such group, Hickson 44. The galaxy group is about 100 million
   light-years distant, far beyond the spiky foreground Milky Way stars,
   toward the constellation Leo. The two spiral galaxies in the center of
   the image are edge-on NGC 3190 with its distinctive, warped dust lanes,
   and S-shaped NGC 3187. Along with the bright elliptical, NGC 3193
   (above and left) they are also known as Arp 316. The spiral toward the
   lower right corner is NGC 3185, the 4th member of the Hickson group.
   Like other galaxies in [8]Hickson groups, these show signs of
   distortion and [9]enhanced star formation, evidence of a gravitational
   tug of war that will eventually result in galaxy mergers on a cosmic
   timescale. The merger process is now understood to be a normal part of
   the evolution of galaxies, including [10]our own Milky Way. For scale,
   [11]NGC 3190 is about 75,000 light-years across at the estimated
   distance of Hickson 44.

                      Tomorrow's picture: light-weekend
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    Authors & editors: [23]Robert Nemiroff ([24]MTU) & [25]Jerry Bonnell
                                 ([26]UMCP)
          NASA Official: Amber Straughn [27]Specific rights apply.
              [28]NASA Web Privacy Policy and Important Notices
                A service of: [29]ASD at [30]NASA / [31]GSFC,
                         [32]NASA Science Activation
                           & [33]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2504/ARP316.jpg
   3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
   4. https://app.astrobin.com/u/175892800@qq.com
   5. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1989ApJS...70..687H&db_key=AST&high=39d9fcfee518892
   6. http://www.deep-sky.co.uk/observing/galaxies/hickson.htm
   7. https://app.astrobin.com/u/175892800@qq.com?i=47pbiv#gallery
   8. https://asterisk.apod.com/viewtopic.php?f=29&t=25085
   9. https://apod.nasa.gov/apod/ap061024.html
  10. https://apod.nasa.gov/apod/ap220606.html
  11. https://apod.nasa.gov/apod/ap100503.html
  12. https://apod.nasa.gov/apod/ap250403.html
  13. https://apod.nasa.gov/apod/archivepix.html
  14. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  15. https://apod.nasa.gov/apod/lib/aptree.html
  16. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  17. https://apod.nasa.gov/apod/calendar/allyears.html
  18. https://apod.nasa.gov/apod.rss
  19. https://apod.nasa.gov/apod/lib/edlinks.html
  20. https://apod.nasa.gov/apod/lib/about_apod.html
  21. http://asterisk.apod.com/discuss_apod.php?date=250404
  22. https://apod.nasa.gov/apod/ap250405.html
  23. http://www.phy.mtu.edu/faculty/Nemiroff.html
  24. http://www.phy.mtu.edu/
  25. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  26. http://www.astro.umd.edu/
  27. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  28. https://www.nasa.gov/about/highlights/HP_Privacy.html
  29. https://astrophysics.gsfc.nasa.gov/
  30. https://www.nasa.gov/
  31. https://www.nasa.gov/centers/goddard/
  32. https://science.nasa.gov/learners
  33. http://www.mtu.edu/