Complex sentence: Comet Kohoutek is a long period comet; its previous apparition was about 150,000 years ago, and its next apparition will be in about 75,000 years.
Split into simpler sentences: Comet Kohoutek is a long period comet. But actually it has a long period, its previous apparition was about 150,000 years ago, and its next apparition will be in about 75,000 years.