Facebook unveiled a new tool Thursday aimed at helping journalists using the social network track breaking and trending news, in a challenge to Twitter. The service called Signal, which is available for both Facebook and the Facebook-owned Instagram platform, is designed for journalists who are using social media as part of their reporting efforts. "We've heard from journalists that they want an easy way to make Facebook a more vital part of their newsgathering with the ability to surface relevant trends, photos, videos, and posts on Facebook and Instagram for use in their storytelling and reporting," Facebook's Andy Mitchell wrote in a blog post. "Today we're excited to introduce Signal, for Facebook and Instagram, a free discovery and curation tool for journalists who want to source, gather and embed newsworthy content from Facebook and Instagram, across news, culture, entertainment, sports, and more - all in one place."With Signal, journalists "can monitor which topics are trending and then quickly display related content that has been shared publicly." Journalists can also access lists of public figures ranked by who is being mentioned the most on Facebook, including "real-time conversations" involving politicians, authors, actors, musicians, athletes and others.The tool can also be used on Instagram for visual content, according to Mitchell. "Every Facebook post, every Instagram image or video, and every metric found in Signal can be easily saved into custom collections for later use," he wrote. "This is a first step in helping journalists use Facebook and Instagram more effectively and we'll gather feedback and iterate to make Signal as useful as possible for industry professionals."