 Before listing all the sources I used to make this 2015 update, I'd like to point to two websites you might find interesting. One is Galaxy Zoo. It's a site where you help with over a million cataloged Hubble Galaxy images. Hany's Varoup was found just this way by Dutch schoolteacher Hany Van Arkel. The name is Dutch for Hany's object. Amazing Space, Hubble's sister site, is launching a new look and feel. Amazing Space takes users on a journey of astronomical discovery through the nearby and distant cosmos, from the combined perspective of the Hubble Space Telescope and its successor, the James Webb Space Telescope. Take a look. And here are two articles worth reading. This is Fritz Swiggy's 1937 paper that first introduces the idea of dark matter. You'll find that it needs some amount of mathematics to understand. The second paper is a recent article by Vera Rubin that you'll find easier to read. And don't forget, every video segment on the How Far Away Is It YouTube channel, including this one, has a document with the text, pictures, links, and notes located on howfarawayisit.com slash documents. Here are the links to the Hubble and other locations where I found the information contained in this 2015 update. These are the places you can go to learn more. Thank you for watching.