News organizations had the most influence on the top Twitter topics in 2010 but some celebrities were not far behind, according to new research.

Alok Choudhary, the chair of the electrical engineering and computer science department at Northwestern University in Illinois, and his team analyzed the biggest trends on Twitter last year.

They found that the Gulf oil spill, the earthquake in Haiti and the Chilean mine rescue were among the top events on Twitter and that singer Lady Gaga, actor Mel Gibson and pop idol Justin Bieber were the most tweeted about people.

NPR News, The New York Times, Times.com and The Wall Street Journal were often the top influencers on politics and world events, but actor Adam Lambert, comedian Conan O'Brien and singer Ricky Martin also had an impact.

"When it comes to world affairs, politics and those types of issues, these major news organizations seem to come on top as major influencers," Choudhary said.

But in tragic situations celebrities can reign on Twitter.

"For the topic of Haiti ... singer Adam Lambert was the most influential tweeter. For the Chilean miner rescue topic, comedian Conan O'Brien was the most influential, and singer Ricky Martin was number two," he added.

A celebrity is more likely to have an impact on a major event if he or she has a large, active following on Twitter, if they are credible and also have a passionate interest in what they are tweeting about, according to Choudhary.

His results are based on a website he developed, www.pulseofthetweeters.com, to rank the most influential tweeters using massive data mining of texts, network analysis and real-time response measures.

He said more than 75 percent of the tweets in 2010 about Lady Gaga and Bieber were positive. But those for Gibson, who made headlines last year when angry voicemails he allegedly made to the mother of his baby daughter were released, were mostly negative.

Bieber was also the top tweeter influencer about the television show "CSI," but the top trending topic was about Bieber's acting role on the show.

Choudhary said basketball player Lebron James, quarterbacks Brett Favre and Michael Vick and Wimbledon and England football team Manchester United were the main sports topics but there was no clear influencer, unlike E! Online, which had the most impact on award shows such as the Grammys and The American Music Awards.