The internal structures of high‐mass and low‐mass stars are thus essentially reversed from each other (see Figure 1). A star of 0.2 solar masses may take a trillion years to use up all its hydrogen. As the white dwarf emits radiation it’s cooling down. For example, Carbon-14 in Earth's atmosphere is produced this way. current age of universe: approx 15,000,000,000 years red dwarf lifetime: 1,000,000,000,000 years There hasn't been time yet for a single very low-mass star to use up all its hydrogen, so we can't check to see if our models are correct! The larger its mass, the shorter its life cycle. In the outer layers of a low‐mass star, the dominant mode of energy transport becomes convective motion. Once the ejected outer layers of the low-mass star become part of the interstellar medium, its hot core is left behind and the low-mass star has entered in the White Dwarf stage. Low mass stars spend billions of years fusing hydrogen to helium in their cores via the proton-proton chain.They usually have a convection zone, and the activity of the convection zone determines if the star has activity similar to the sunspot cycle on our Sun. Main Sequence. A new star will sit at a specific point on the main sequence of the Hertzsprung–Russell diagram, with the main-sequence spectral type depending upon the mass of the star. Iron for high mass stars. Most of this interaction is with low-weight elements, so it produces other low-weight elements. Some small stars have very deep convection zones. A white dwarf star is the leftover core of a low-mass star. Low-mass stars are generally cooler and dimmer than their higher-mass counterparts. Figure 1; High‐mass versus low‐mass main sequence structure. 20% of the Sun's helium comes from CNO catalyst nucleosynthesis, but I suspect that oxygen, carbon, and nitrogen was already in the Sun when nuclear ignition took place. Life Cycles of Stars A star's life cycle is determined by its mass. Oxygen, maybe, for low mass stars. So, simply by looking at a star's color, temperature, and where it "lives" in the Hertzsprung-Russell diagram, astronomers can get a good idea of a star's mass. The conditions inside a star that allow the formation of the higher mass elements can be related to a pushing match between gravity and the energy released by the star. A star's mass is determined by the amount of matter that is available in its nebula, the giant cloud of gas and dust from which it was born.Over time, the hydrogen gas in the nebula is pulled together by gravity and it begins to spin.