APOD: 2019 March 19 - Abell 370: Galaxy Cluster Gravitational Lens

                         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.

                                2019 March 19
                                      [2]
                Abell 370: Galaxy Cluster Gravitational Lens
    Image Credit: NASA [3] , ESA [4] , Hubble [5] ; Processing & Copyright:
              Rogelio Bernal Andreo [6] (DeepSkyColors.com [7] )

Explanation: What are those strange arcs? While imaging the cluster of
galaxies Abell 370, astronomers noticed an unusual arc. The arc wasn't
understood right away -- not until better images showed that the arc was a
previously unseen type of astrophysical [8]  artifact of a gravitational lens
[9] , where the lens was the center of an entire cluster of galaxies [10] .
Today, we know that this arc [11] , the brightest arc in the cluster, actually
consists of two distorted images [12]  of a fairly normal galaxy that happens
to lie far in the distance. Abell 370's gravity [13]  caused the background
galaxies' light -- and others -- to spread out and come to the observer along
multiple paths [14] , not unlike a distant light appears through the stem of a
wine glass [15] . Almost all of the yellow images featured here [16]  are
galaxies in the Abell 370 cluster. An astute eye [17]  can pick up many
strange arcs [18]  and distorted arclets [19] , however, that are actually
gravitationally lensed [20] images of distant normal galaxies [21] . Studying
Abell 370 [22] and its images gives astronomers a unique window into the
distribution of normal and dark [23] matter [24]  in galaxy clusters [25]  and
the universe.

                Tomorrow's picture: welcome to the equinox [26]

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    Authors & editors: Robert Nemiroff [38] (MTU [39] ) & Jerry Bonnell [40]
                                  (UMCP [41] )
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                           & Michigan Tech. U. [47]
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Site notes:
  [1] archivepix.html
  [2] image/1903/Abell370Arcs_HubbleAndreo_1840.jpg
  [3] https://www.nasa.gov/
  [4] https://www.esa.int/About_Us/Welcome_to_ESA
  [5] https://www.nasa.gov/mission_pages/hubble/sto...
  [6] https://en.wikipedia.org/wiki/Rogelio_Bernal_...
  [7] http://www.deepskycolors.com/
  [8] https://science.gsfc.nasa.gov/astrophysics/
  [9] http://en.wikipedia.org/wiki/Gravitational_le...
  [10] ap180326.html
  [11] ap990104.html
  [12] http://adsabs.harvard.edu/abs/1999A%26A...347...
  [13] http://spaceplace.nasa.gov/what-is-gravity/en...
  [14] http://www.youtube.com/watch?v=BkBNf_nFuhM
  [15]
http://wela.astro.ulg.ac.be/themes/extragal/g...
  [16] https://www.flickr.com/photos/deepskycolors/4...
  [17] https://thumbs.dreamstime.com/z/cat-myopia-27...
  [18] ap080210.html
  [19] ap090823.html
  [20] https://arxiv.org/abs/astro-ph/9312003
  [21] ap180305.html
  [22] http://en.wikipedia.org/wiki/Abell_370
  [23] http://en.wikipedia.org/wiki/Dark_matter
  [24] http://chandra.harvard.edu/xray_astro/dark_ma...
  [25] ap070516.html
  [26] ap190320.html
  [27] ap190318.html
  [28] archivepix.html
  [29] lib/apsubmit2015.html
  [30] lib/aptree.html
  [31] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apo...
  [32] calendar/allyears.html
  [33] /apod.rss
  [34] lib/edlinks.html
  [35] lib/about_apod.html
  [36] http://asterisk.apod.com/discuss_apod.php?dat...
  [37] ap190320.html
  [38] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [39] http://www.phy.mtu.edu/
  [40] https://antwrp.gsfc.nasa.gov/htmltest/jbonnel...
  [41] http://www.astro.umd.edu/
  [42] lib/about_apod.html#srapply
  [43] https://www.nasa.gov/about/highlights/HP_Priv...
  [44] https://astrophysics.gsfc.nasa.gov/
  [45] https://www.nasa.gov/
  [46] https://www.nasa.gov/centers/goddard/
  [47] http://www.mtu.edu/

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