NASA has shortlisted four proposals for its next astrophysics missions, due for launch in 2025. The agency has funding to fly two of them, and the four will now each receive funds for a nine-month period of technical study. The two missions will be chosen next year.
Galaxy clusters are among the largest structures in the universe, containing thousands of individual galaxies, dark matter and hot gas. At the heart of the Ophiuchus cluster there is a large galaxy that contains a supermassive black hole with a mass equivalent to 10 millions suns.