Enlarge Image Facebook

Live streaming video has become a cause du jour of Silicon Valley. Now Facebook's joining the fray -- but there's a hitch: You have to be a celebrity to use it.

The world's largest social network is launching a new feature it simply calls "Live," designed to allow celebrities and public figures to stream video to the nearly 1.5 billion people who log onto the site per month.

The service works out of Facebook's Mentions app, which launched last year and is designed to help celebrities more easily post and respond to comments, likes and other messages sent their way by fans.

"Whether you have an established fan base or want to build up your audience, Live is a new way for you to connect authentically with your fans in the moment," Vadim Lavrusik, a product manager at Facebook, wrote in a blog post announcing the feature Wednesday.

The move ups Facebook's competition against a group of new live-video apps that have gotten a lot of attention in the tech world over the past couple months.

Meerkat, which lets people live-broadcast videos from their phones, launched in February and gained popularity during the South by Southwest tech festival in Texas the following month. The startup also raised $12 million in venture capital. That same time, Twitter introduced its own competing live-video app, Periscope, which The Wall Street Journal said it purchased for $100 million.

There's also Snapchat, which, though it hasn't focused on live video, is designed to allow users to easily share short videos with friends and other users on the network, using a feature called "Stories."

Whether live video is the next great boom in social networking or merely a fad is still unclear. Twitter said in April that it counted over 1 million people who had logged into the app within its first 10 days on the market, while Meerkat in May said it counted nearly 2 million users on its service. Neither though have indicated how frequently users connect with their services.

For now, Facebook will try to stand out by focusing on celebrities, and it's already lined up plans for broadcasts by actor Dwayne "The Rock" Johnson, pro tennis player Serena Williams, news broadcaster Lester Holt and lifestyle maven Martha Stewart.

The company didn't respond to a request for comment about whether it's planning to make the feature available to the rest of the site's users.

"With Live, public figures can take fans behind the scenes, host a Q&A, share announcements, and more -- all in real time," Lavrusik wrote in his blog post.