The early phase of a star, once gas and dust begin to coalesce into a sphere, is called a protostar.

Here's a breakdown:

* Gas and Dust Cloud: The process begins with a large cloud of gas and dust in space, often called a nebula.

* Gravitational Collapse: Over time, these clouds can become unstable and begin to collapse under their own gravity.

* Protostar Formation: As the cloud collapses, the material in the center becomes denser and hotter. This hot, dense core is the protostar.

* Evolution to a Star: The protostar continues to grow and heat up, eventually reaching a point where nuclear fusion begins in its core. This marks the birth of a true star.

So, the protostar is essentially the "baby" stage of a star, before it reaches the point where it can sustain itself through fusion.