How does an astronomical object become a star?

What process must the astronomical object perform to be considered a star?

Answer:

An astronomical object is considered a star primarily through the process of fusion of hydrogen into helium in its core during its lifecycle.

Explanation:

The process an astronomical object must undergo to be classified as a star is the fusion of hydrogen into helium which is option A. From a general understanding of star formation, all the materials forming a star come from the core which surrounds the forming star made up of dense cores of gas and dust within a large clump. As the gravitational force of the infalling gas becomes strong enough and far outweighs the pressure exerted by the cold material forming the dense cores, the material undergoes a swift collapse and the density of the core becomes significantly increased. During this time when the dense core is contracting to transform into a star and before the fusion of hydrogen to form helium begins, we refer to the object as a protostar.

At some point in the lifecycle of a star, after they have morphed into red giants, the cores of these stars become sufficiently heated to generate energy through fusing helium to form carbon. For stars with masses about twice that of the Sun or lesser, the fusion process halts after the helium in the core has been spent. In such instances, the fusion of hydrogen and helium in shells around the contracting core makes the star a bright red giant again, however temporarily.