The mass is usually a surprise finding when a chest X-ray is done for reasons unrelated to the cancer.

CNN: What is Hodgkin lymphoma's effect on the lymphatic system?

"Wise is finding them across the full sky, while Nustar is giving us an entirely new look at their high-energy X-ray light and learning what makes them tick, " he said.

BBC: Supermassive black holes and hot galaxies in giant haul