Musicians and fans will now be privy to a whole new metric of success, thanks to Billboard, who is today launching the Social 50, a chart that measures an artist’s popularity based on social networking activity.

Last March, we introduced you to Next Big Sound, a tool that gauges an artist’s popularity based on fan activity across sites like FacebookFacebook, YouTubeYouTube, MySpaceMySpace, TwitterTwitter, iLike, WikipediaWikipedia, Soundcloud, Reverb Nation, Pure Volume, OurStage, VimeoVimeo, BeboBebo, Amie Street, Jam Legend and VirbVirb.

Now the service is getting a shot of old media cache, as it will be providing data to Billboard that will be used to compile the weekly Social 50 chart.

Like NBS, the Social 50 will rank artists using such metrics as weekly additions of friends, fans and followers (depending on the network), artist page views and weekly song plays. Rankings are also influenced by measuring the ratio of page views to fans.

Predictably, artists present on the debut chart are largely mainstream, the top 10 including Rihanna (who holds the number-one spot and recently nabbed two Grammy nominations) and Eminem’s “Lovelove the Way You Lie,” YouTube darlings Justin Bieberjustin bieber and Lady Gaga, and Twitter fave Nicki Minaj. Oft-parodied Ke$ha and social media-savvy Katy Perry also made the cut.

“We continue to adapt the way we chart the changing landscape of music,” says Billboard Editorial Director Bill Werde. “The Social 50 is yet another step in the evolution of Billboard and an important response to our changing times.”

Image courtesy of iStockphotoiStockphoto, deeAuvil