How Did this Unusual Supernova Form? (IMAGE) Carnegie Institution for Science Caption This cartoon courtesy of Anthony Piro illustrates three possibilities for the origin of the mysterious hydrogen emissions from the Type IA supernova called ASASSN-18tb that were observed by the Carnegie astronomers. Starting from the top and going clockwise: The collision of the explosion with a hydrogen-rich companion star, the explosion triggered by two colliding white dwarf stars subsequently colliding with a third hydrogen-rich star, or the explosion interacting with circumstellar hydrogen material. Credit Courtesy of Anthony Piro, Carnegie Institution for Science Usage Restrictions With credit 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.