                         Astronomy Picture of the Day

                         Astronomy Picture of the Day

    Discover the cosmos! [1] Each day a different image or photograph of our
 fascinating universe is featured, along with a brief explanation written by a
                           professional astronomer.

                              2018 September 17
                                      [2]
                    Cosmic Collision Forges Galactic Ring
Image Credit: X-ray: Chandra [3] (NASA [4] , CXC [5] , INAF [6] , A. Wolter et
            al. [7] ); Optical: Hubble [8] (NASA [9] , STScI [10] )

Explanation: How could a galaxy become shaped like a ring? The rim of the blue
galaxy pictured [11] on the right is an immense ring-like structure 150,000
light years [12]  in diameter composed of newly formed, extremely bright,
massive stars. That galaxy, AM 0644-741 [13] , is known as a ring galaxy [14]
and was caused by an immense galaxy collision. When galaxies collide [15] ,
they pass through each other -- their individual stars rarely come into
contact. The ring [16] -like shape is the result of the gravitational
disruption [17]  caused by an entire small intruder [18]  galaxy passing
through a large one. When this happens, interstellar gas and dust [19]  become
condensed, causing a wave of star formation [20] to move out from the impact
point like a ripple across the surface of a pond. The likely intruder galaxy
is on the left of this combined image from Hubble [21] (visible [22] ) and
Chandra [23] (X-ray [24] ) space telescopes. X-ray light is shown in pink and
depicts places [25]  where energetic black holes or neutron stars [26] ,
likely formed shortly after the galaxy collision [27] , reside.

Open Science: Browse 1,800+ codes in the Astrophysics Source Code Library [28]

                    Tomorrow's picture: a rose for a swan

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Site notes:
  [1] archivepix.html
  [2] image/1809/Ring0644_HubbleChandra_3348.jpg
  [3] http://chandra.harvard.edu/index.html
  [4] https://www.nasa.gov/
  [5] http://chandra.harvard.edu/about/
  [6] http://www.media.inaf.it/tag/chandra/
  [7] https://arxiv.org/abs/1806.02746
  [8] https://www.nasa.gov/mission_pages/hubble/story/index.html
  [9] https://www.nasa.gov/
  [10] http://www.stsci.edu/
  [11] http://chandra.si.edu/photo/2018/ring/
  [12] http://chandra.harvard.edu/photo/cosmic_distance.html
  [13] http://adsabs.harvard.edu/abs/1997ApJ...474..686H
  [14] ap010612.html
  [15] ap150201.html
  [16] http://en.wikipedia.org/wiki/Engagement_ring
  [17] http://en.wikipedia.org/wiki/Tidal_force
  [18]
https://s-media-cache-ak0.pinimg.com/736x/5b/60/1e/
5b601e8413f01f169a27dffd3a1e1601.jpg
  [19] ap030706.html
  [20] http://astronomy.swin.edu.au/cosmos/D/density+wave+model
  [21] http://www.stsci.edu/hst/HST_overview/
  [22] https://science.nasa.gov/ems/09_visiblelight
  [23] https://www.nasa.gov/mission_pages/chandra/main/index.html
  [24] https://science.nasa.gov/ems/11_xrays
  [25] https://www.youtube.com/watch?v=FgbmB_yLbZ0
  [26] https://apod.nasa.gov/htmltest/rjn_bht.html
  [27] ap130514.html
  [28] http://ascl.net/code/all
  [29] ap180916.html
  [30] archivepix.html
  [31] lib/apsubmit2015.html
  [32] lib/aptree.html
  [33] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  [34] calendar/allyears.html
  [35] /apod.rss
  [36] lib/edlinks.html
  [37] lib/about_apod.html
  [38] http://asterisk.apod.com/discuss_apod.php?date=180917
  [39] ap180918.html
  [40] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [41] http://www.phy.mtu.edu/
  [42] https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  [43] http://www.astro.umd.edu/
  [44] lib/about_apod.html#srapply
  [45] https://www.nasa.gov/about/highlights/HP_Privacy.html
  [46] https://astrophysics.gsfc.nasa.gov/
  [47] https://www.nasa.gov/
  [48] https://www.nasa.gov/centers/goddard/
  [49] http://www.mtu.edu/
