NGC 4921: A Ram Pressure Stripped Galaxy (IMAGE) National Radio Astronomy Observatory Caption Shown here in composite view, ALMA data (red/orange) reveals filament structures left behind by ram pressure stripping in a Hubble Space Telescope optical view of NGC 4921. Scientists believe that these filaments are formed as magnetic fields in the galaxy prevent some matter from being stripped away. Credit ALMA (ESO/NAOJ/NRAO)/S. Dagnello (NRAO), NASA/ESA/Hubble/K. Cook (LLNL), L. Shatz Usage Restrictions No restrictions. License Public Domain 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.