Complex sentence: At these temperatures, it is called the "Warm-Hot Intergalactic Medium (WHIM)"; and computer simulations indicate that on the order of half the atomic matter in the universe might exist in this warm-hot, rarified state.
Split into simpler sentences: At these temperatures, it is called the Warm-Hot Intergalactic Medium (WHIM). Computer simulations indicate that on the order of half the atomic matter in the universe might exist in this warm-hot, rarified state.