             APOD: 2017 October 2 - Two Comets and a Star Cluster

                         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 2
                                      [2]
                        Two Comets and a Star Cluster
                Image Credit & Copyright [3] : Damian Peach [4]

Explanation: Two unusual spots are on the move near the famous Pleiades star
cluster. Shifting only a small amount per night, these spots [5]  are actually
comets [6] in our nearby Solar System that by chance wandered into the field
of the light-year [7] s distant stars. On the far left is comet C/2017 O1 [8]
ASAS-SN, a multi-kilometer block of evaporating ice sporting a bright coma [9]
 of surrounding gas dominated by green-glowing [10]  carbon. Comet ASAS-SN1
[11] shows a slight tail to its lower right. Near the frame center is comet
C/2015 ER61 PanSTARRS [12] , also a giant block of evaporating ice [13] , but
sporting a rather long tail [14]  to its right. On the upper right is the
Pleiades [15] , an open cluster [16] dominated by bright blue stars
illuminating nearby reflecting dust [17] . This exposure, taken about two
weeks ago, is so deep that the filamentary interstellar dust can be traced
across the entire field [18] . The Pleiades is visible to the unaided eye [19]
, but it should require binoculars to see the comets [20] .

                      Tomorrow's picture: star ring [21]

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    Authors & editors: Robert Nemiroff [33] (MTU [34] ) & Jerry Bonnell [35]
                                  (UMCP [36] )
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Site notes:
  [1] archivepix.html
  [2] image/1710/PleiadesComets_Peach_2081.jpg
  [3] lib/about_apod.html#srapply
  [4] http://www.damianpeach.com/
  [5] ap170923.html
  [6] https://solarsystem.nasa.gov/planets/comets
  [7]
https://www.grc.nasa.gov/www/k-12/Numbers/Math/Mathematical_Thinking/
how_long_is_a_light_year.htm
  [8]
https://www.universetoday.com/136564/
new-comet-c2017-o1-asas-sn-takes-earth-surprise/
  [9] ap170212.html
  [10] https://briankoberlein.com/2015/01/25/easy-green/
  [11] https://en.wikipedia.org/wiki/ASASSN1
  [12] https://en.wikipedia.org/wiki/C/2015_ER61_(PANSTARRS)
  [13] https://www.youtube.com/watch?v=JoH7sdCaa4g
  [14] ap150227.html
  [15] ap150617.html
  [16] open_clusters.html
  [17] ap101118.html
  [18]
http://www.wikisky.org/
?ra=3.875798551649525&de=23.
55138728835037&zoom=5&show_grid=1&show_constellation_lines=1&show_
constellation_boundaries=1&show_const_names=0&show_galaxies=1&show_box=1&box_
ra=3.7833333&box_de=24.116667&box_width=469.33248&box_height=469.
33248&box_var_size=1&img_source=DSS2
  [19]
https://i.pinimg.com/736x/ae/48/10/
ae4810cdeb095bcc229611a592e65537--funny-vintage-pictures-funny-photos.jpg
  [20] http://cometchasing.skyhound.com/
  [21] ap171003.html
  [22] ap171001.html
  [23] archivepix.html
  [24] lib/apsubmit2015.html
  [25] lib/aptree.html
  [26] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  [27] calendar/allyears.html
  [28] /apod.rss
  [29] lib/edlinks.html
  [30] lib/about_apod.html
  [31] http://asterisk.apod.com/discuss_apod.php?date=171002
  [32] ap171003.html
  [33] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [34] http://www.phy.mtu.edu/
  [35] https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  [36] http://www.astro.umd.edu/
  [37] lib/about_apod.html#srapply
  [38] https://www.nasa.gov/about/highlights/HP_Privacy.html
  [39] https://astrophysics.gsfc.nasa.gov/
  [40] https://www.nasa.gov/
  [41] https://www.nasa.gov/centers/goddard/
  [42] http://www.mtu.edu/
