Gas giant mass more quickly via hydrodynamic escape than larger planets and planets farther out. A gas dwarf could be defined as a planet with a rocky core that has accumulated a thick envelope of hydrogen, helium and other volatiles, having as result a total radius between 1.7 and 3.9 Earth-radii. The smallest known extrasolar planet that is likely a "gas planet" is Kepler-138d, which has the same mass as Earth but is 60% larger and therefore has a density that indicates a thick gas envelope. A low-mass gas planet can still have a radius resembling that of a gas giant if
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