Every second, more than 3,000 stars are born in the visible universe. Many are surrounded by what astronomers call a protoplanetary disk—a swirling “pancake” of hot gas and dust from which planets form. The exact processes that give rise to stars and planetary systems, however, are still poorly understood. Every second, more than 3,000 stars are born in the visible universe. Many are surrounded by what astronomers call a protoplanetary disk—a swirling “pancake” of hot gas and dust from which planets form. The exact processes that give rise to stars and planetary systems, however, are still poorly understood. Planetary Sciences Phys.org – latest science and technology news stories