Like low-mass stars, high-mass stars are born in nebulae and evolve and live in the Main Sequence. A massive star will undergo a supernova explosion. It is by far the most important source of energy for life on Earth. And just a few million years later, it settled down into its current form. A star will enjoy most of its life in the main sequence phase. On the right of the illustration is the life cycle of a massive star (10 times or more the size of our Sun). The Sun is the star at the center of the Solar System.It is a nearly perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. Life Cycle of a Star Credit: NASA. However, their life cycles start to differ after the red giant phase. The path they follow beyond that depends on the mass of the star. The Sun started as a T Tauri star – a wildly active star that blasted out an intense solar wind. If the star is big enough to fuse hydrogen atoms into helium, it will enter the phase that our Sun is in, called the main sequence phase. The life cycle of a Sun-like star (annotated) This image tracks the life of a Sun-like star, from its birth on the left side of the frame to its evolution into a red giant star on the right. Its diameter is about 1.39 million kilometers (864,000 miles), or 109 times that of Earth, and its mass is about 330,000 times that of Earth. On the left the star is seen as a protostar, embedded within a dusty disc of material as it forms.