             APOD: 2017 September 28 - LIGO Virgo GW170814 Skymap

                         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.

                              2017 September 28
                                      [2]
                          LIGO-Virgo GW170814 Skymap
  Illustration Credit: LIGO [3] - Virgo [4]  Collaboration - Optical Sky Data:
                                 A. Mellinger

Explanation: From around planet Earth [5] three gravitational wave detectors
have now reported a joint detection of ripples in spacetime, the fourth
announced detection of a binary black hole merger in the distant Universe. The
event [6] was recorded on 2017 August 14, and so christened GW170814, by the
LIGO observatory [7]  sites in Hanford, Washington and Livingston, Louisiana,
and the more recently operational Virgo Observatory near Pisa, Italy. The
signal was emitted in the final moments of the coalescence [8]  of two black
holes [9]  of 31 and 25 solar masses located about 1.8 billion light-years
away. But comparing [10] the timing of the gravitational wave detections at
all three sites allowed astronomers to vastly improve the location of the
signal's origin on the sky. Just above the Magellanic clouds and generally
toward the constellation Eridanus, the only sky region consistent with signals
in all three detectors is indicated by the yellow contour line in this all-sky
map. The all-sky projection includes the arc of our Milky Way Galaxy [11] . An
improved three-detector location of the gravitational wave [12]  source
allowed rapid follow-up observations by other, more conventional,
electromagnetic wave observatories that can search for potentially related
signals. The addition of the Virgo detector also allowed the gravitational
wave polarization to be measured, a property that further confirms predictions
of [13]  Einstein's general relativity.

                  Tomorrow's picture: supernova remnant [14]

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    Authors & editors: Robert Nemiroff [26] (MTU [27] ) & Jerry Bonnell [28]
                                  (UMCP [29] )
          NASA Official:  Phillip Newman Specific rights apply [30] .
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              A service of: ASD [32]  at NASA [33]  / GSFC [34]
                           & Michigan Tech. U. [35]
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Site notes:
  [1] archivepix.html
  [2] image/1709/GW170814_orig.png
  [3] https://www.ligo.caltech.edu/
  [4] http://www.virgo-gw.eu/
  [5] http://www.virgo-gw.eu
  [6] http://www.virgo-gw.eu/docs/GW170814/
  [7] https://www.ligo.caltech.edu/news/ligo20170927
  [8] ap160212.html
  [9] ap170602.html
  [10] http://www.virgo-gw.eu/skymap.html
  [11] ap091125.html
  [12] https://spaceplace.nasa.gov/gravitational-waves/en/
  [13] https://en.wikipedia.org/wiki/
Sticky_bead_argument#Einstein.27s_double_reversal
  [14] ap170929.html
  [15] ap170927.html
  [16] archivepix.html
  [17] lib/apsubmit2015.html
  [18] lib/aptree.html
  [19] http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  [20] calendar/allyears.html
  [21] /apod.rss
  [22] lib/edlinks.html
  [23] lib/about_apod.html
  [24] http://asterisk.apod.com/discuss_apod.php?date=170928
  [25] ap170929.html
  [26] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [27] http://www.phy.mtu.edu/
  [28] http://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  [29] http://www.astro.umd.edu/
  [30] lib/about_apod.html#srapply
  [31] http://www.nasa.gov/about/highlights/HP_Privacy.html
  [32] http://astrophysics.gsfc.nasa.gov/
  [33] http://www.nasa.gov/
  [34] http://www.nasa.gov/centers/goddard/
  [35] http://www.mtu.edu/
