V391 Pegasi the ejection of the hydrogen envelope of a red giant star at or just before the onset of helium fusion. The ejection left only a tiny amount of hydrogen on the surface - less than 1/1000 of the total stellar mass. The future for the star is to eventually cool down to make a low mass white dwarf. Most stars retain more of their hydrogen after the first red giant phase, and eventually become asymptotic giant branch stars. The reason that some stars, like V391 Pegasi, lose so much mass is not well known. In 2007, a gas giant planet
Hydrogen gas porosity concentration in the gas is measured and converted into a reading of the gas concentration in the metal. This method is fast, reproducible and accurate, and can be used “on-line” on the cast shop floor. The amount of H in the gas loop of the instrument is determined by a thermal conductivity sensor, which provides high reproducibility and a broad measurement range. 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