         APOD: 2017 October 3 - Ice Ring around Nearby Star Fomalhaut

                         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 October 3
                                      [2]
                    Ice Ring around Nearby Star Fomalhaut
  Image Credit: ALMA (ESO/NAOJ/NRAO), M. MacGregor; NASA/ESA Hubble, P. Kalas;
                           B. Saxton (NRAO/AUI/NSF)

Explanation: Why is there a large ice ring around Fomalhaut? This interesting
star [3]  -- easily visible in the night sky -- lies only about 25 light-years
[4]  away and is known to be orbited by at least one planet, Dagon [5] , as
well as several inner dust disks. More intriguing, perhaps, is an outer ring
[6] , first discovered about 20 years ago, that has an unusually sharp inner
boundary. The featured recent image [7]  by the Atacama Large Millimeter Array
[8]  (ALMA) shows this outer ring with complete and unprecedented detail -- in
pink -- superposed on a Hubble [9] image of the Fomalhaut system in blue. A
leading theory holds [10]  that this ring resulted from numerous violent
collision [11] s involving icy comets [12]  and planetesimals [13] , the
component objects of planets [14] , while the ring boundaries are caused by
the gravity [15]  of yet unseen planets. If correct, any interior planets in
the Fomalhaut system [16]  are likely being continually pelted by large
meteors and comets -- an onslaught last seen in our own planetary system [17]
four billion years ago in an episode called the Late Heavy Bombardment [18] .

                  Free Download: The 2018 APOD Calendar [19]
                      Tomorrow's picture: soul sky [20]

-------------------------------------------------------------------------------
< [21] | Archive [22] | Submissions [23] | Index [24] | Search [25] | Calendar
  [26] | RSS [27] | Education [28] | About APOD [29] | Discuss [30] | > [31]
-------------------------------------------------------------------------------

    Authors & editors: Robert Nemiroff [32] (MTU [33] ) & Jerry Bonnell [34]
                                  (UMCP [35] )
          NASA Official:  Phillip Newman Specific rights apply [36] .
              NASA Web Privacy Policy and Important Notices [37]
              A service of: ASD [38]  at NASA [39]  / GSFC [40]
                           & Michigan Tech. U. [41]
----------
Site notes:
  [1] archivepix.html
  [2] image/1710/FomalhautRing_ALMA_2064.jpg
  [3] https://en.wikipedia.org/wiki/Fomalhaut
  [4]
https://www.grc.nasa.gov/www/k-12/Numbers/Math/Mathematical_Thinking/
how_long_is_a_light_year.htm
  [5] https://en.wikipedia.org/wiki/Fomalhaut_b
  [6] ap050701.html
  [7]
http://www.almaobservatory.org/en/press-release/
alma-eyes-icy-ring-around-young-planetary-system/
  [8] http://www.almaobservatory.org/en/about-alma-at-first-glance/
  [9] https://www.nasa.gov/mission_pages/hubble/story/index.html
  [10] http://adsabs.harvard.edu/abs/2017ApJ...842....8M
  [11] https://www.youtube.com/watch?v=XWkfckzpk1E
  [12] ap150203.html
  [13] http://www.lpi.usra.edu/education/timeline/gallery/slide_3.html
  [14] https://www.youtube.com/watch?v=UNPj7e6XJCQ
  [15] ap041217.html
  [16]
http://earthsky.org/brightest-stars/solitary-fomalhaut-guards-the-southern-sky
  [17] https://solarsystem.nasa.gov/planets/solarsystem
  [18] https://en.wikipedia.org/wiki/Late_Heavy_Bombardment
  [19] https://apod.nasa.gov/apod/fap/APOD_Calendar_2018_300dpi.pdf
  [20] ap171004.html
  [21] ap171002.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=171003
  [31] ap171004.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/
