Cardinals are returning to the Sistine Chapel for a second day of voting to choose a new pope after their first ballot yielded no winner and a great plume of black smoke emerged from the Sistine Chapel chimney.

Pilgrims gather in St Peter's Square ( Jeff J Mitchell/Getty Images)

The schedule for Wednesday's voting includes a brief prayer followed by two rounds of morning balloting from the 115 cardinals. If no one gets the necessary 77 votes, cardinals break for lunch and return for two more ballots in the afternoon.

The drama — with stage sets by Michelangelo and an outcome that is anyone's guess — is playing out against the backdrop of the turmoil unleashed by Benedict XVI's surprise resignation and the exposure of deep divisions among cardinals. As a result, many analysts predict a long conclave