                   APOD: 2018 July 11 - Symbiotic R Aquarii

                         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 July 11
                                      [2]
                             Symbiotic R Aquarii
  Image Credit: Hubble [3] , NASA [4] , ESA [5] ; Processing & License [6] :
                               Judy Schmidt [7]

Explanation: You can see it change in brightness with just binoculars over the
course of a year. Variable star R Aquarii [8] is actually an interacting
binary star system, two stars that seem to have a close, symbiotic
relationship [9] . About 710 light years away, this intriguing system consists
of a cool red giant star [10]  and hot, dense white dwarf star [11]  in mutual
orbit around their common center of mass. The binary system's visible light is
dominated by the red giant, itself a Mira [12] -type long period variable star
[13] . But material in the cool giant star's extended envelope is pulled by
gravity onto the surface of the smaller, denser white dwarf, eventually
triggering [14]  a thermonuclear explosion [15]  and blasting material into
space. The featured image [16]  from the Hubble Space Telescope [17]  shows
the still-expanding ring of debris which spans less than a light year [18]
and originated from a blast that would have been seen in the early 1770s. The
evolution of [19]  less understood energetic events producing high energy
emission in the R Aquarii [20] system has been monitored since 2000 using
Chandra X-ray Observatory [21]  data.

                      Tomorrow's picture: open space [22]

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    Authors & editors: Robert Nemiroff [34] (MTU [35] ) & Jerry Bonnell [36]
                                  (UMCP [37] )
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Site notes:
  [1] archivepix.html
  [2] image/1807/Raquarii_HubbleSchmidt_3116.jpg
  [3] https://www.nasa.gov/mission_pages/hubble/main/index.html
  [4] https://www.nasa.gov/
  [5] http://www.esa.int/
  [6] https://creativecommons.org/licenses/by/2.0/
  [7] http://geckzilla.com/
  [8] https://www.aavso.org/vsots_raqr
  [9] http://chandra.harvard.edu/photo/2017/raqr/
  [10] https://en.wikipedia.org/wiki/Red_giant
  [11] https://imagine.gsfc.nasa.gov/science/objects/dwarfs2.html
  [12] ap060722.html
  [13] https://www.aavso.org/public
  [14] ap060726.html
  [15] https://www.youtube.com/watch?v=RZKiWGT4Za4
  [16] https://www.flickr.com/photos/geckzilla/37736684446/in/dateposted/
  [17]
https://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/
what-is-the-hubble-space-telecope-58.html
  [18] https://spaceplace.nasa.gov/light-year/en/
  [19] http://chandra.harvard.edu/photo/2017/raqr/animations.html
  [20] https://en.wikipedia.org/wiki/R_Aquarii
  [21] http://chandra.harvard.edu/index.html
  [22] ap180712.html
  [23] ap180710.html
  [24] archivepix.html
  [25] lib/apsubmit2015.html
  [26] lib/aptree.html
  [27] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  [28] calendar/allyears.html
  [29] /apod.rss
  [30] lib/edlinks.html
  [31] lib/about_apod.html
  [32] http://asterisk.apod.com/discuss_apod.php?date=180711
  [33] ap180712.html
  [34] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [35] http://www.phy.mtu.edu/
  [36] https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  [37] http://www.astro.umd.edu/
  [38] lib/about_apod.html#srapply
  [39] https://www.nasa.gov/about/highlights/HP_Privacy.html
  [40] https://astrophysics.gsfc.nasa.gov/
  [41] https://www.nasa.gov/
  [42] https://www.nasa.gov/centers/goddard/
  [43] http://www.mtu.edu/
