This envelope gradually peters out with altitude . 这一包层随高度而逐渐稀薄。
The outer part of the envelope now has the form of a thick shell or dust cocoon . 现在包壳的外层部分是厚壳层或尘埃包层的形状。
It is not clear whether the envelope is ejected in many small spurts or all at once . 包层的抛射究竟是通过多次小喷溅,还是一次全部抛出,这并不清楚。
At the point c, the star develops a convection zone extending from near the surface deep into the extended envelope . 在C点,星体产生一个对流区,从表面附近向内扩展到广袤的包层。
When helium burning takes over the main burden of energy generation in the star, the core expands somewhat, and the envelope contracts somewhat . 当氦燃烧成为星体能量产生的主要来源时,核心略微膨胀,而包层略微收缩。