Astronomers have long speculated that the missing baryonic mass might eventually be discovered in intergalactic space or as some large population of galaxies that are difficult to detect.
天文学家长期以来都在推测，最终可能会在星际空间或者是在难以探测的大量星系中发现丢失的重子质量。
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These galaxies may constitute an answer to the long-standing puzzle of the missing baryonic mass in the universe.
这些星系可能为宇宙中长期存在的缺少重子质量这一谜题提供了答案。
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Dark matter: this generally refers to "exotic" non-baryonic matter that interacts only weakly with ordinary matter.