Sternberg has already started in his new role and and is overseeing the club's MUTV channel, websites, mobile, social and print media.
His appointment does not affect the position of United's communications director Phil Townsend.
United have a hugely popular Facebook page but do not yet have a Twitter account. However, the club displayed its future intentions in its handling of Sir Alex Ferguson's retirement as manager.
The official news release carried the hashtag #thankyousiralex and his decision to retire led to 1.4million mentions in an hour on Twitter, more than the death of former Prime Minister Margaret Thatcher.