▁place ▁in ▁ 1 4 5 6 . ▁ ▁According ▁to ▁one ▁story ▁that ▁first ▁appeared ▁in ▁a ▁ 1 4 7 5 ▁post hum ous ▁bi ography ▁and ▁was ▁subsequently ▁emb ell ished ▁and ▁popular ized ▁by ▁Pierre - Sim on ▁Lap lace , ▁Cal li xt us ▁III ▁ex communic ated ▁the ▁ 1 4 5 6 ▁appearance ▁of ▁Hal ley ' s ▁Com et , ▁bel ieving ▁it ▁to ▁be ▁an ▁ill ▁o men ▁for ▁the ▁Christian ▁def enders ▁of ▁Bel grade ▁from ▁the ▁bes ie ging ▁arm ies ▁of ▁the ▁Ott oman ▁Empire . ▁No ▁known ▁primary ▁source ▁supports ▁the ▁authentic ity ▁of ▁this ▁account . ▁The ▁ 2 9 ▁June ▁ 1 4 5 6 ▁pap al ▁b ull ▁of ▁Cal li xt us ▁III ▁calling ▁for ▁a ▁public ▁prayer ▁for ▁the ▁success ▁of ▁the ▁cr us ade ▁makes ▁no ▁mention ▁of ▁the ▁com et . ▁By ▁ 6 ▁August , ▁when ▁the ▁Turkish ▁sie ge ▁was ▁broken , ▁the ▁com et ▁had ▁not ▁been ▁visible ▁in ▁either ▁Europe ▁or ▁Turkey ▁for ▁several ▁weeks . ▁ ▁Death ▁ ▁Cal li xt us ▁III ▁died ▁on ▁ 6 ▁August ▁ 1 4 5 8 . ▁His ▁remains ▁were ▁transferred ▁in ▁ 1 5 8 6 ▁and ▁again ▁in ▁ 1 6 1 0 ▁with ▁the ▁remains ▁of ▁his ▁nep hew ▁Alexander ▁VI ▁to ▁Santa ▁Maria ▁in ▁Mon ser r ato . ▁His ▁remains ▁were ▁transferred ▁once ▁more ▁on ▁ 2 1 ▁August ▁ 1 8 8 9 ▁in ▁the