If ice were more dense than water, it would freeze and sink over and over until the entire lake was frozen. ... This same process occurs in the fall as the surface water cools and becomes more dense; it will sink and cause the same movement or turnover of the lake's water.
Answer: The contracting cloud is then called a protostar. A protostar is the earliest stage of a star's life. A star is born when the gas and dust from a nebula become so hot that nuclear fusion starts.