The only word you should capitalize is "A", at the beginning of the sentence. There are no proper nouns that would have to be capitalized.
adverb phrase
Yes, from the remains of a supernova and from the outer layers of gas shed through a black dwarf.
The end of fusion. With nothing left to convert, the star's remains collapse inward on themselves. The tremendous heat and pressure caused by this rapidly creates all natural elements heavier than iron, and releases the most immense amount of energy in heat and light known in the universe. Much of the elements created are blown off into interstellar space, and the collapsed remains become a neutron star, the densest object in the universe, unless it was an exceptionally large star to begin with, then the remains become a Black Hole.
Our sun is not a first generation star, so the gases and other materials that clumped together to form our solar system came from the remains of the previous generation. There is no telling how many supernovas contributed to the materials that make our system (and us) up, but the number is very large; possibly in the millions. Scientists may have ways to estimate the number, but we will never really know.
"Stellar masses" is not a unit of mass - perhaps you mean "solar masses". Depending on the remaining mass - after the supernova explosion - either a neutron star or a black hole. In the case of four stellar masses, probably a neutron star; it would require a more massive star than that to become a black hole.
Remains from all the astronauts were recovered.
after a supernova
Adverb Phrase ..
We believe this to be true, even though we cannot yet prove this.
No. No planet is massive enough to become a black hole. A black hole is the remains of a dead, supermassive star.
Because it IS a supernova remnant. It's the visial remains of a star that expolded and was seen in 1054. Designated SN 1054.
A neutron star, or a black hole. Which it is, depends on the mass that remains after the supernova explosion. Above a certain mass limit, a black hole will form.
If sufficient mass remains after the supernova explosion, it will become a black hole.
A pulsar is a rapidly-spinning neutron star, the remains of a supernova explosion.
Yes, from the remains of a supernova and from the outer layers of gas shed through a black dwarf.
Generally, "and" remains in lower case; e.g. Pride and Prejudice.
It won't - it doesn't have enough mass. But if any star converts to a supernova, it will destroy its planetary system in the process, and even cause damage to nearby solar systems (should they have life, it would be in grave peril). After the supernova phase, what remains of the star would normally convert to a neutron star, or a black hole.
The white dwarf collapses under its own gravity. This starts very rapid nuclear fusion reactions. It explodes as a supernova and "stuff" is scattered into space. Essentially nothing of the white dwarf, as an object, remains.