Echo'ing variables into page.tpl.php

I would like to manually add Facebook's Open Grpah meta information into page.tpl.php (no modules). What is the syntax to echo these variables?

og:title - The title of your object as it should appear within the graph, e.g., "The Rock".
og:type - The type of your object, e.g., "movie". See the complete list of supported types.
og:image - An image URL which should represent your object within the graph. The image must be at least 50px by 50px and have a maximum aspect ratio of 3:1. We support PNG, JPEG and GIF formats. You may include multiple og:image tags to associate multiple images with your page.
og:url - The canonical URL of your object that will be used as its permanent ID in the graph, e.g., http://www.imdb.com/title/tt0117500/.

Any ideas?