Complex sentence: Another unusual aspect is the fact that scientists are observing this Galaxy at a time when the Universe was only a little over 1.4 billion years old, meaning that this Galaxy was exhibiting the strange behaviour while the Universe was still in its infancy.
Split into simpler sentences: Another unusual aspect is the fact that scientists are observing this Galaxy at a time when the Universe was only a little over 1.4 billion years old. Meaning that this Galaxy was exhibiting the strange behaviour while the Universe was still in its infancy.