The Big Bang Theory season 9
The Big Bang Theory season 9 premieres on 21 September CBS

CBS has released the official synopsis for The Big Bang Theory season 9 premiere episode which will pick up in Las Vegas and feature Leonard (Johnny Galecki) and Penny's (Kaley Cuoco-Sweeting) nuptials as Sheldon (Jim Parsons) deals with his breakup with Amy. The 9th season-opener episode is titled The Matrimonial Momentum, which will air on 21 September on CBS Network. The official synopsis reads as follows:

After driving to Vegas to get married, Penny struggles with Leonard's confession that he kissed another girl. Also, Sheldon doesn't know how to act after Amy pushes pause on their relationship, on the ninth season premiere of The Big Bang Theory. Laurie Metcalf returns as Sheldon's mother, Mary.

Previously, The Hollywood Reporter had unveiled the first look at Leonard and Penny's wedding, where showrunner Steve Molaro dished on the couple's married life. "Chuck and I had a long talk about [revealing the wedding before the premiere] and my fear was that it was going to start sound like they didn't [get married]," Molaro told the publication.

"That was not a positive message — and we didn't want fans to feel like, 'Oh, they're going to pull the rug again and not do it.' There is so much more story beyond that moment that we decided to just let people know," he added.

But it will not be all smooth sailing for the newly-weds after Leonard reveals that he kissed Mandy while on a North Sea expedition. When asked if Penny is still hurt by Leonard's revelation, Molaro teased, "A little bit, yeah. She thinks she's OK with it and she may not be."

The producer added, "It's the kind of thing that you wouldn't expect to happen and that can be a little jarring. I think when you're Penny, and you have an image that you've cultivated of a person for eight years now and those two things aren't aligning anymore — that can be a difficult thing to deal with."

Meanwhile Sheldon, who was dumped by Amy in the season 8 finale, will not be happy about Leonard and Penny's wedding. Fans of the hit series know that Sheldon left town after Leonard proposed to Penny, and asked him to move out in the season 7 final episode. But now that Leonard and Penny are married, it will be interesting to see what living arrangements they'll work out.

"Living arrangements are definitely going to be confronted in the first four episodes. It's tricky, sure — Leonard and Penny need to move forward, but at the same time we have a broken-hearted Sheldon), who is sort of their little brother and child and it's tough to ignore that for them."

So, is Sheldon heartbroken over Leonard and Penny's wedding? We have to wait till The Big Bang Theory returns for season 9 on 21 September for the answer to that question.