What is #19: A Protostar?

The 'What Is' Series

A couple of months ago I started a new series on this blog titled "What Is". Thus far the focus is on the field of astronomy where we hear all sorts of cool science taking place in space. The goal of this series is to explain the details of different objects we hear about relatively frequently.

A Protostar

I've spent a lot of time in this series talking about different types of stars. This includes Red Giants, White Dwarfs, and Neutron Stars to name just a few. Another type of star is a Protostar. The word 'proto' means first or beginning, so a Protostar is a beginning star, or to be more clear, a star before it is officially a star. A star is defined as a large ball of gas that fuses hydrogen into helium in its core. Before a star reaches this stage, it is called a Protostar.

Protostar Herbig-Haro 46/47 - NASA-JPL

Stars start out as large molecular clouds of gas. A molecular cloud, or part of a molecular cloud can collapse. As the gas collapses, the temperature of the ball of gas starts to increase. If it increases to the point of emitting infrared radiation, we call it a Protostar. Some Protostars will become hot enough to be official stars fusing hydrogen. If the star doesn't reach a high enough temperature to fuse, it becomes a Brown Dwarf. 

To conclude, a Protostar is a potential star before it becomes a star.