What is the Rarest Thing?

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What is the least common “thing” in the universe?

http://helios.gsfc.nasa.gov/nucleo.html (Nucleosynthesis explanation)
http://www.stanford.edu/~sehlert/Supernovae.pdf (Supernova nucleosynthesis)
http://abyss.uoregon.edu/~js/ast122/lectures/lec13.html (Star Formation)
http://en.wikipedia.org/wiki/Isotopes_of_hydrogen (Isotopes of Hydrogen)
http://en.wikipedia.org/wiki/Iron_peak (Fusion beyond iron)
http://en.wikipedia.org/wiki/Synthesis_of_precious_metals (Synthesis of precious metals)
http://periodictable.com/Elements/Radioactive/ (List of radioactive elements)
http://en.wikipedia.org/wiki/List_of_elements_by_stability_of_isotopes (List of elements by stability of isoptopes)
http://www.chemicool.com/elements/astatine.html (Astatine)
http://www.britannica.com/EBchecked/topic/252386/half-life (Explanation of Half-life)
http://scienceblogs.com/startswithabang/2009/04/03/is-uranium-the-heaviest-natura/ (Is Uranium really the heaviest naturally occurring element?)
http://books.google.com.bh/books?id=MfAGpVq8gpQC&pg=PA119&dq=transuranic+elements+supernova&redir_esc=y#v=onepage&q=transuranic%20elements%20supernova&f=false (Says that Super heavy elements form in supernovae)
http://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements (Abundance of the chemical elements)
http://www.webelements.com/ununoctium/ (Ununoctium Summary)
http://en.wikipedia.org/wiki/Antimatter (Antimatter)
http://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter(Gravitational interaction of antimatter)
http://www.sciencedaily.com/releases/2011/06/110605132431.htm (Trapping anti-hydrogen)
http://www.sciencedaily.com/releases/2011/04/110424152441.htm (Heaviest synthesized Anti-element created, Antihellium-4)
http://www.sciencedaily.com/releases/2011/07/110727161135.htm (Fundamental Matter-Antimatter Symmetry Confirmed)
http://www.sciencedaily.com/releases/2012/08/120815082719.htm (Article about the Island of stability)
http://en.wikipedia.org/wiki/Ununennium (Unnunennium)
http://en.wikipedia.org/wiki/Unbinilium (Unbinilium)
http://en.wikipedia.org/wiki/Unbihexium (Unbihexium)
http://arxiv.org/pdf/1103.3312v2.pdf (Anti-Hellium Atoms)

Credits:
Some space footage has been collected from Space Engine:
http://en.spaceengine.org/

Damek – http://commons.wikimedia.org/wiki/File:3D_anamation_of_the_Rutherford_atom.ogv

DePiep -http://commons.wikimedia.org/wiki/File:Periodic_table_(polyatomic).svg#mediaviewer/File:Periodic_table_(polyatomic).svg

US Mint – http://en.wikipedia.org/wiki/American_Silver_Eagle#mediaviewer/File:Liberty_$1_Reverse.png
Us Mint – http://en.wikipedia.org/wiki/Dollar_coin_(United_States)#mediaviewer/File:Sacagawea_Obverse.png
Us Mint – http://commons.wikimedia.org/wiki/File:American_Platinum_Eagle_2007_Rev.jpg

Bill Saxton, NRAO/AUI/NSF – http://cdn.phys.org/newman/gfx/news/hires/2012/astronomersg.jpg

The material around SN 1987A par ESO/L. Calçada – http://commons.wikimedia.org/wiki/File:The_material_around_SN_1987A.jpg#mediaviewer/Fichier:The_material_around_SN_1987A.jpg

NASA – http://www.youtube.com/watch?v=UNPj7e6XJCQ

GregRobson – http://commons.wikimedia.org/wiki/File:Electron_shell_085_astatine.png#globalusage

Webelements – http://www.webelements.com/astatine/isotopes.html

ESO/L. Calçada – ESO -http://commons.wikimedia.org/wiki/File:Artist%E2%80%99s_Impression_of_a_Baby_Star_Still_Surrounded_by_a_Protoplanetary_Disc.jpg#mediaviewer/File:Artist%E2%80%99s_Impression_of_a_Baby_Star_Still_Surrounded_by_a_Protoplanetary_Disc.jpg

CERN – http://cds.cern.ch/record/1610170

CERN – http://cds.cern.ch/record/1354957

Pumbaa – http://commons.wikimedia.org/wiki/File:Electron_shell_119_Ununennium.svg

Pumbaa – http://commons.wikimedia.org/wiki/File:Electron_shell_120_Unbinilium.svg

Pumbaa – http://commons.wikimedia.org/wiki/File:Electron_shell_126_Unbihexium_-_no_label.svg

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