A hydrogen envelope refers to a layer of hydrogen gas that surrounds or encloses something, like a planet or a star. It is like a protective layer made up of hydrogen gas. Full definition
Its outer hydrogen envelope becomes more loosely bound and vulnerable to gravitational stripping, or a type of stellar cannibalism, by the nearby companion star. (sciencedaily.com)
Another way Wolf - Rayet stars are said to form is when a massive star ejects its own hydrogen envelope in a strong stellar wind streaming with charged particles. (sciencedaily.com)
The one GOOD thing about these direct hits would be ELIMINATION of thick Hydrogen envelopes around these types of planets when these envelopes were HEATED by MUCH MORE LUMINOUS HOST STARS to the point where the envelopes FILLED the planets» Hill spheres. (centauri-dreams.org)