         APOD: 2017 August 7 - Spiral Galaxy NGC 1512: The Inner Ring

                         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 August 7
                                      [2]
                    Spiral Galaxy NGC 1512: The Inner Ring
        Image Credit: NASA [3] , ESA [4] , Hubble Space Telescope [5]

Explanation: Most galaxies don't have any rings -- why does this galaxy have
two? To begin, the bright band near NGC 1512 [6] 's center is a nuclear ring
[7] , a ring that surrounds the galaxy center and glows brightly with recently
formed stars [8] . Most stars and accompanying gas and dust [9] , however,
orbit the galactic center in a ring much further out -- here seen near the
image edge. This ring is called, counter-intuitively [10] , the inner ring. If
you look closely, you will see this the inner ring connects [11]  ends of a
diffuse central bar [12] that runs horizontally across the galaxy. These ring
structures are thought to be caused by NGC 1512 [13] 's own asymmetries in a
drawn-out process called secular evolution [14] . The gravity [15]  of these
galaxy asymmetries, including the bar of stars, cause gas and dust to fall
from the inner ring to the nuclear ring, enhancing this ring's rate of star
[16]  formation. Some spiral galaxies [17] also have a third ring -- an outer
ring that circles [18]  the galaxy even further out.

       Two Weeks from Today: An American total eclipse of the Sun [19]
                   Tomorrow's picture: waves of Saturn [20]

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    Authors & editors: Robert Nemiroff [32] (MTU [33] ) & Jerry Bonnell [34]
                                  (UMCP [35] )
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Site notes:
  [1] archivepix.html
  [2] image/1708/NGC1512inner_Hubble_5413.jpg
  [3] https://www.nasa.gov/
  [4] http://www.esa.int/
  [5] https://www.nasa.gov/mission_pages/hubble/story/index.html
  [6] https://en.wikipedia.org/wiki/NGC_1512
  [7] ap170710.html
  [8] https://en.wikipedia.org/wiki/Star_formation
  [9] ap030706.html
  [10] http://www.guy-sports.com/fun_pictures/cat_curious_wall.jpg
  [11] http://adsabs.harvard.edu/abs/2017ApJS..230...14M
  [12] ap160109.html
  [13] http://www.spacetelescope.org/news/heic1712/
  [14] http://adsabs.harvard.edu/abs/2004ARA%26A..42..603K
  [15] ap150112.html
  [16]
https://starchild.gsfc.nasa.gov/docs/StarChild/universe_level2/stars.html
  [17] ap150526.html
  [18]
https://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/
what-is-orbit-58.html
  [19] https://eclipse2017.nasa.gov/
  [20] ap170808.html
  [21] ap170806.html
  [22] archivepix.html
  [23] lib/apsubmit2015.html
  [24] lib/aptree.html
  [25] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  [26] calendar/allyears.html
  [27] /apod.rss
  [28] lib/edlinks.html
  [29] lib/about_apod.html
  [30] http://asterisk.apod.com/discuss_apod.php?date=170807
  [31] ap170808.html
  [32] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [33] http://www.phy.mtu.edu/
  [34] https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  [35] http://www.astro.umd.edu/
  [36] lib/about_apod.html#srapply
  [37] https://www.nasa.gov/about/highlights/HP_Privacy.html
  [38] https://astrophysics.gsfc.nasa.gov/
  [39] https://www.nasa.gov/
  [40] https://www.nasa.gov/centers/goddard/
  [41] http://www.mtu.edu/
