Jennifer Lopez and Aerosmith frontman Steven Tyler will join Randy Jackson as American Idol judges next season, after months of speculation about the future of US TV’s top-rated show.

With pomp rivalling that of a US Supreme Court appointment, Fox finally assembled the new pieces of the Idol panel that will be returned to its original three-member format for season 10.

Actress-singer-dancer Jennifer and Steven will have the job of trying to match the offbeat chemistry of former judges Simon Cowell and Paula Abdul.

“This is American Idol,” host Ryan Seacrest said after the new trio took the stage with him.

Steven said he wanted to join the show because “it’s being a part of something much bigger than yourself. … I want to bring some rock to this rollercoaster and show if you’ve got the heart, the talent, the feeling to do this you could be the next American Idol”.

“I’m so excited,” Lopez said. “I’m looking for the next Michael Jackson.”

Simon announced last January that he planned to leave to launch a new talent show for Fox in 2011, with newcomers Ellen DeGeneres and Kara DioGuardi exiting this summer.

Paula left in 2009 over a contract dispute.

Randy will be the only original judge when American Idol returns in January.

Jennifer and Steven could help American Idol reinvent itself for the new season, when it will try to stem a ratings slide and bring in younger viewers.

The show’s audience has been gradually ageing, and advertisers prefer to pitch to young adults.