Complex sentence: The energy being radiated by this star is creating an H II region in the neighboring volume of space, which is surrounded in turn by an expanding ring of cool gas that has an age of about 2--6 million years.
Split into simpler sentences: The energy being radiated by this star is creating an H II region in the surrounding volume. Surrounding this is an expanding ring of cool gas with an age of about 2--6 million years.