Turning Hydrogen into Helium

Until a protostar has reached the Main Sequence, its chemical composition remains unchanged. It consists, as it has since it began life as a part of a molecular cloud, almost entirely of hydrogen gas. Once core temperatures have reached critical temperatures of more than 

however, that situation changes. Hydrogen nuclei (protons) can begin to fuse and form helium nuclei. This process is sometimes known as hydrogen burning. The term is technically incorrect because there is no combustion involved in the process. It is widely used, however, as a shorthand description of the nuclear changes that take place. 

That fusion process occurs in three steps that can be summarized by three relatively simple nuclear equations. In the following equations, hydrogen is represented by its chemical symbol, H. Remember, however, that at the very high temperatures of a star s core, hydrogen is completely ionized and exists only as protons. 

Note that it is possible to obtain the net reaction that occurs during fusion by deleting species that occur on both sides of the above three equations. Before doing so, however, notice that the last step (Step 3) can occur only after steps 1 and 2 have first occurred twice. That is, two helium-3 nuclei are required in order for Step 3 to occur. Therefore, it is necessary for Step 2 (and, of course, Step 1) to have taken place twice to produce that many helium-3 nuclei. The net reaction for the fusion of hydrogen into helium, then, can be calculated as follows  

The above reactions might appear to be relatively simple and straightforward, but the nuclear equations given here do not reveal all of the details as to how hydrogen fuses into helium in these reactions. One of the most difficult problems is explaining how two positively charged particles—the two protons in Step 1—can get close 

---

Never mind. In the center of the Sun is the core, the Sun s power plant in which nuclear fusion reactions turn hydrogen into helium and generate tremendous amounts of heat. Here, the gas density is more than 100 times that of water, or 14 times that of lead. In fact, the core contains 40 percent of the solar mass. 2 Sir, at that density, why isn t the core a solid ... 

Finally let us turn to the new periodic table, which it is claimed restores a fundamental role to triads. Rather than relocating helium to the. alkaline earths and thereby losing a perfect triad (He, Ne, Ar), we propose to relocate hydrogen into the halogen group, thereby gaining one completely new perfect triad (H, F, Cl) as shown in Figure 3-... 

There are, however, some difficulties about this theory. One is that there are no stable nucleides with mass 5 or mass 8, and thus no synthesis of the elements beyond these masses through neutron capture alone is possible the synthesis stops when all of the hydrogen has been turned into helium 4. 

---