Comparison of a UDG to a Spiral Galaxy (IMAGE) W. M. Keck Observatory Caption DGSAT I (left), an ultra-diffuse galaxy (UDG), is shown next to a normal spiral galaxy (right) for comparison. Both are similar in size, but UDGs like DGSAT I have so few stars, you can see right through them, to the galaxies in the background. Credit A. ROMANOWSKY/UCO/D. MARTINEZ-DELGADO/ARI Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.