Red giant and the creation of a planetary nebula finally ends the red-giant phase of the star's evolution. The red-giant phase typically lasts only around a billion years in total for a solar mass star, almost all of which is spent on the red-giant branch. The horizontal-branch and asymptotic-giant-branch phases proceed tens of times faster. If the star has about 0.2 to , it is massive enough to become a red giant but does not have enough mass to initiate the fusion of helium. These "intermediate" stars cool somewhat and increase their luminosity but never achieve the tip of the red-giant branch
Hydrogen gas porosity Hydrogen gas porosity Hydrogen gas porosity is an aluminium casting defect under the form of a porosity or void in an aluminium casting caused by a high level of hydrogen gas (H) dissolved in the aluminium at liquid phase. Because the solubility of hydrogen in solid aluminium is much smaller than in liquid aluminium, when the aluminium freezes, the dissolved hydrogen gas creates porosity in solid aluminium. Aluminum smelters and aluminum foundries want to produce high quality aluminum and shape castings with minimum porosity. This can be obtained by reducing the amount of hydrogen in the liquid aluminium alloy. Hydrogen