Exploring the Cosmos - Class Test 3 - Life and Death of Stars (Part 1)
1. Primordial elements were created early on
in all of the above.
in the life of stars.
in the history of the Universe.
in the life of planets like Earth.
2. In the proton-proton chain, how many hydrogen nuclei are necessary to produce a helium nucleus by nuclear fusion reactions?
Sixteen
Four
Eight
Two
3. Why are conditions ideal for neutron capture deep inside evolved stars?
Heavy nuclei are rich in neutrons and tend to attract more neutrons than light nuclei.
Neutrons are a by-product of many nuclear reactions, so there are many free neutrons available to interact with nuclei.
Hydrogen nuclei are the most abundant deep inside stars and can capture neutrons very easily.
The temperature is high enough to overcome repulsive forces between nuclei and free neutrons.
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