Pope Leo XIV will be the Catholic Church's 267th leader.
VATICAN CITY -- Robert Prevost of the United States has been named the new pope, the new head of the Catholic church.
Cardinals gathered to select their latest leader during a conclave.
White smoke poured out of the Sistine Chapel chimney Thursday at 6:07 p.m. local time, signaling that a pontiff had been elected to lead the Catholic Church.
(The Associated Press and ABC News contributed to this report.)
Cardinal Robert Prevost, an American missionary who spent his career ministering in Peru and leads the Vatican's powerful office of bishops, was elected the first American pope in the 2,000-year history of the Catholic Church.
Prevost, 69, took the name Leo XIV.
Take a look at photos from Vatican City as it is announced that Pope Leo XIV is the next pontiff.
Cardinal Robert Francis Prevost has become the first-ever American elected as the leader of the Catholic Church -- now known by his pontifical name of Pope Leo XIV.
The 69-year-old, born on the Southside of Chicago, is seen as a diplomat of the church and was an important adviser to his predecessor, Pope Francis.
He became a front-runner to the papacy in the days before the conclave began, said the Rev. James Martin, a papal contributor to ABC News.
Leo emerged from the balcony of St. Peter's Basilica on Thursday evening to throngs of cheering crowds, following the signal of white smoke that emanated from the chimney atop the Sistine Chapel.
Leo is the fifth-most-popular name chosen by popes. Pope Leo XIV's full authority and jurisdiction begins immediately upon his acceptance of the office.
READ MORE | What we know about Leo XIV, the new American pope
White smoke was seen emanating from the chimney of the Sistine Chapel, indicating that a two-thirds vote has been reached to elect the new pope.
Thousands of people cheered in Vatican Square when the smoke appeared.
What is the science behind the smoke signals on the Sistine Chapel to announce if a new pope has been elected?
Dr. Olivia Castellini, senior exhibit strategist at the Griffin Museum of Science, says chemicals are added to the fire to slow down the combustion reaction and create smoke.
"When it is a black fire, they add in potassium perchlorate, anthracene and sulfur," Dr. Castellini said. "So the potassium perchlorate is bringing the oxygen to the party because that is one of the ingredients for our combustion. The anthracite is going to be our fuel, it doesn't like to burn completely so you put some sulfur in there to help things along. So you actually end up using up the oxygen before the fuel, so you get a lot of soot that comes out and the soot is black.
The white smoke is a slightly different chemical composition.
"You have calcium chlorate, which again is going to bring that oxygen, you use lactose, which is just sugar," Dr. Castellini said. "Sugar burns really quickly, very cleanly, so you get a clean smoke coming out. And they also add pine resin, which used to be called pitch, so that has a lot of water. You have a lot of water and particles that come out. You are basically making an artificial cloud."
Black smoke emerged from the chimney of the Sistine Chapel during the conclave.
That meant that no new pope had been elected by the cardinals.
It signified the end of the second round of voting -- and three ballots -- with no consensus.
The cardinals planned to take a break for lunch before beginning their next round of voting.
Eyewitness News Anchor Joe Torres reports from the Vatican.
An estimated 45,000 people gathered in St Peter's Square to await the results of the first conclave vote, which had been expected some time after 7 p.m. but ended up coming in around 9 p.m., according to Vatican News.
After failing to come to a consensus, the College of Cardinals have gathered on Thursday morning for the second day of conclave, with up to four more opportunities for them to select the 267th pope.
-ABC News' Phoebe Natanson
