Question

nucleosynthesis in a massive star worksheet
use the generalized nucleosynthesis in a massive star diagram to answer the following questions.
part 1: multiple choice

1. which stage of nuclear fusion is the longest in a massive star?

a) carbon fusing into oxygen
b) helium fusing into carbon
c) hydrogen fusing into helium
d) silicon fusing into iron

1. according to the diagram, what does oxygen (o) fuse into?

a) carbon
b) silicon (si)
c) iron (fe)
d) helium (he)

1. in a massive star, how long does the fusion of (carbon to oxygen) last?

a) 600 years
b) 6 months
c) 1 day
d) ¼ second
part 2: fill - in - the - blanks

1. the stage of fusing helium into carbon lasts for 700,000 years.
2. once the stars core is made of iron, it can no longer generate energy from fusion.
3. the process of creating heavier elements by fusing the smaller atoms inside a star is known as nucleosynthesis.
4. as you go deeper into the stars core, the temperature and pressure both increase.

part 3: short answer

1. why does the duration of each fusion stage become so much shorter as the star gets older and creates heavier elements? due to temperature and pressure increasing
2. what happens immediately after the core turns to iron and why does it happen so quickly (in 1/4 of a second)?
3. what is the ultimate fate of all the heavy elements (like oxygen, carbon, and iron) created inside the massive star after it explodes as a supernova?

Explanation:

1. In massive stars, hydrogen - to - helium fusion is the longest as it is the first and most abundant fuel source.
2. Oxygen fuses into silicon in the nucleosynthesis process of a massive star.
3. The carbon - to - oxygen fusion in a massive star lasts about 600 years.
4. Helium - to - carbon fusion lasts around 700,000 years.
5. Once the core is iron, fusion stops as iron fusion consumes energy instead of producing it.
6. The process of creating heavier elements from lighter ones in a star is nucleosynthesis.
7. Deeper in the star's core, higher temperature and pressure are needed for successive fusion stages.
8. As the star ages and creates heavier elements, the temperature and pressure increase, causing fusion to occur faster.
9. After the core turns to iron, a supernova explosion occurs rapidly because the core collapses under gravity, causing a shock - wave that blows off the outer layers of the star.
10. After a supernova explosion, heavy elements are dispersed into space and can be part of new star and planet formations.

Answer:

1. c) Hydrogen fusing into Helium
2. b) Silicon (Si)
3. a) 600 years
4. 700,000
5. iron
6. nucleosynthesis
7. increase
8. Due to temperature and pressure increasing
9. A supernova explosion occurs because the core collapses under gravity, creating a shock - wave that blows off the outer layers of the star.
10. They are dispersed into space and can be part of new star and planet formations.