Explain how most astronomers believe stars are born?

They believe that a cloud of gas (nebula) starts being pulled together by gravity to the point where it is so small, it starts nuclear fusion. This then start the stars life.

Answerd. may include all of these are many definitions of bases: the  brønsted-lowry definition of acids and bases says that bases are proton acceptors.the arrhenius definition of acids and bases says that bases increase [oh⁻] in solution (thereby producing oh⁻ ions)the lewis definition of acids and bases says that bases donate electron pairs.therefore, the sensible answer is that a base may include all of the described characteristics.