Some of the fabric essential for sprightliness as we get it on it — iron , atomic number 19 , and iodine , for deterrent example — are created by supernovae and then distributed throughout blank space . But these stellar explosions also create lead , silver , and gold , as well as heavy radioactive element like atomic number 92 and plutonium . “ little amounts of rubble from these distant explosions fall on the Earth as it travels through the galaxy,”saysAustralian National University ’s Anton Wallner .
To determine the amount of heavy elements in what they thought was supernova debris in the deep ocean , Wallner and colleagues dissect a 10 - centimeter - thick sample of the Earth ’s impertinence ( image above ) that represents two dozen million year of accretion , as well as deposit collected from a stable area at the bottom of the Pacific Ocean . They focus on plutonium-244 , which play like a clock thanks to the nature of its radioactive decline : It has a half - life of 81 million yr . They were surprised .
“ We ’ve analyzed galactic rubble from the last 25 million year that has patch up on the ocean and found there is much less of the big component such as Pu and uranium than we carry , ” Wallner says in anews release . “ We found 100 time less plutonium-244 than we expect . ”
Any plutonium-244 that existed when our planet formed from intergalactic gas and dust over four billion years ago has long since dilapidate . Wallner add : “ So any plutonium-244 that we chance on earth must have been make in explosive events that have fall out more lately , in the last few hundred million eld . ”
Thefindings , write inNature Communicationsthis calendar week , advise that the heaviest elements were n’t shape in standard supernovae . Rather , this discrepancy indicates that the laboured , radioactive phallus of the periodic table were created in much rarer , more volatile result — such as the merging of twoneutron stars(pictured to the right ) , each of which may contain the mass of the Lord’s Day in a domain the size of a city .
range of a function : A. Wallner et al . , Nature Communications 2015 ( top),NASA / Goddard Space Flight Center(bottom )
