Gas Halo (IMAGE) W. M. Keck Observatory Caption This is an artist's concept showing the gaseous halo surrounding a galaxy, illuminated by a narrow band of ultraviolet light called Lyman alpha emission. BX418's gas halo is about ten times the size of the galaxy itself. Credit Tonia Klein, UWM 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.