To explain this, they hypothesise that galaxies must contain a great deal of missing matter which cannot be detected.为了解释这一点，他们假定各星系一定包含了大量无法探测到的不明物质。They hypothesise that galaxies must contain a great deal of missing matter which cannot be detected.他们假定各星系必然含有大量无法探测到的失踪物质。