Complex sentence: Theta Carinae is a single-lined spectroscopic binary with a period of 2.2 days; the shortest known orbital period among massive stars, suggesting the possibility that mass transfer between the two components may have occurred, which could explain the peculiarities of the spectrum.
Split into simpler sentences: Theta Carinae is actually a single-lined spectroscopic binary with a period of 2.2 days; the shortest known orbital period among massive stars. The close orbit means that a mass transfer between the two components may have occurred, which could explain the peculiarities of the spectrum.