Western Governors University (WGU) SCIE1020 C165 Integrated Physical Sciences Practice Exam

The formation of a star is a result of nuclear fusion, which is a process that occurs in the cores of stars. Stars begin their lives as clouds of gas and dust, which undergo gravitational collapse. As the material condenses, the temperature and pressure in the core increase significantly. When conditions become favorable, hydrogen nuclei begin to fuse into helium, releasing an immense amount of energy in the process. This energy generates the heat and light characteristic of stars.

In contrast, planets, moons, and black holes do not form through nuclear fusion. Planets and moons form from the residual material around a star that clumps together through gravitational attraction, while black holes are the remnants of massive stars that have exhausted their nuclear fuel and undergone a gravitational collapse, leading to an infinitely dense point. Thus, stars are uniquely defined by their ability to sustain nuclear fusion, setting them apart from these other celestial bodies.