Question

2. The circle of life! Stars are formed in dense molecular clouds. Can stars return the mass to the interstellar space [1 pt)? Please describe two processes that stars return its mass to the interstellar space [2 pts each, 4pts in total). After one cycle, which properties of the interstellar gas have changed [2 pts]?

Answer 1

Yes. Law of Conservation of energy can be clearly seen during the lifetime of a star. Intersteller space is not a closed medium. A star returns the mass to he intersteller space. Gravity stars having the mass of the Sun live for ~10 billion years, but high-mass stars live and die within a few million years. Initially,

The initial stages of stellar evolution for stars includes helium burning. After it exhausts in
the core, the star burns a series of new fuels, mainly carbon, neon, oxygen, and silicon in the
core. As each fuel is exhausted in the core, it begins to burn in a shell around the core, creating layered structure like onion with each layer containing products of different nucleosynthetic burning. When silicon has been consumed in the core, there is no more nuclear fuel to support the star against gravity and it collapses catastrophically resulting in suernova formation with an explosion which ejects the outer and intermediate layers of the star, returning newly synthesized elements to the galaxy. The interior zones collapse back on the remnant, which can be either a neutron star.

Intersteller gases become more or less dense, hotter and colder, and change its state of ionization.