Galaxy Clusters Connected by Gas Bridge (image) European Space Agency Caption Planck has discovered a bridge of hot gas that connects galaxy clusters Abell 399 (lower centre) and Abell 401 (top left). The galaxy pair is located about a billion light-years from Earth, and the gas bridge extends approximately 10 million light-years between them. The image shows the two galaxy clusters as seen at optical wavelengths with ground-based telescopes and through the Sunyaev-Zel'dovich effect (in orange) with ESA's Planck satellite. Credit Sunyaev-Zel'dovich effect: ESA Planck Collaboration; Optical image: STScI Digitized Sky SurveI Usage Restrictions For non-commercial use only. For free use only with full credit line indicated. 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.