How are elements produced in stars after iron?

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In summary, elements are formed in the core of stars where fusion occurs. This happens as the outer layers of the star rebound off of the surface. During this rebound, the temperature, pressure, and density reach a level high enough to cause fusion to occur, building up elements higher than iron/nickel.
  • #1
ajayguhan
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we know that elements are formed in the core of stars where fusion occurs.

The stars collapse on the formation of iron, if it so how come element after iron like cobalt, gold, silver were produced...?
 
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  • #2
As the core collapses, the outer layers of the star fall as well. Once the core reaches sufficient density for neutron-neutron repulsion to hold it up, it stops collapsing and the outer layers of the star rebound off of the surface. During this rebound, the temperature, pressure, and density reach a level high enough to cause fusion to occur, building up elements higher than iron/nickel. Note that this fusion process does NOT release energy. Instead it takes energy, as the heavier elements have less binding energy per nucleon than either iron or nickel.

There is also a large burst of neutrons released, some of which are then captured by the nuclei. Beta decay can then turn some of the neutrons into protons and result in an element with more protons than it had before.

http://en.wikipedia.org/wiki/Supernova_nucleosynthesis
 
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  • #3
Technically, the process of synthesizing elements heavier than iron/nickel is endothermic, as opposed to exothermic, meaning less energy is released than absorbed. You are, however, correct in noting this extra energy is mainly supplied by the shock wave in a core detonation event. Neutrinos contribute to this process in ways not yet fully understood.
 
  • #4
Drakkith said:
During this rebound, the temperature, pressure, and density reach a level high enough to cause fusion to occur, building up elements higher than iron/nickel.

A number of stars have spectral lines of technetium. Technetium is heavier than iron, and is short lived (up to 4 million years) so it could not have been in the stars before, nor have these stars exploded yet.
 
  • #5
snorkack said:
A number of stars have spectral lines of technetium. Technetium is heavier than iron, and is short lived (up to 4 million years) so it could not have been in the stars before, nor have these stars exploded yet.

There is also the s-process, known as slow neutron capture, that takes place in stars. Neutrons produced in the star are captured, building up heavier isotopes of elements until they reach the point that beta decay turns them into the next element by converting a neutron into a proton. Also, see the following link for a paper about the production of technetium.

http://www.nature.com/nature/journal/v337/n6209/pdf/337718a0.pdf
 
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1. What is a supernova?

A supernova is a powerful explosion that occurs at the end of a star's life cycle. It is caused by the sudden collapse of a massive star's core, which releases an enormous amount of energy and creates a bright burst of light.

2. How do supernovae create new elements?

During a supernova, the intense heat and pressure can fuse atoms together, creating heavier elements. Elements such as carbon, oxygen, and iron are formed during the explosion and then dispersed into space, where they can eventually become part of new stars and planets.

3. What elements are created during a supernova?

A wide variety of elements are formed during a supernova, including elements with atomic numbers greater than iron, such as gold and uranium. These elements are not typically formed in the cores of stars, so supernovae are essential for their creation.

4. How does a supernova affect the surrounding environment?

The explosion of a supernova releases large amounts of energy and radiation, which can have a significant impact on the surrounding environment. This can include heating up nearby gas and dust, triggering the formation of new stars, and dispersing elements into the interstellar medium.

5. Can supernovae be dangerous to Earth?

Supernovae that occur within our galaxy are typically not dangerous to Earth because they are far enough away. However, if a supernova were to occur within a certain distance from Earth, it could potentially have harmful effects on our planet's atmosphere and ecosystems. Fortunately, the nearest known supernova candidate is currently over 500 light-years away.

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