₆¹²C + ⁴₂H→ ₈¹⁶O + γ........(15)
¹⁶₈O + ⁴₂He→ ²⁰₁₀ Ne +γ....(16)
The more massive stars (>1.3×10 times the mass of our sun) which have higher internal temperature (>1.7×10⁷ kelvin). The CNO cycle ( carbon-nitrogen - oxygen) can provide alternative synthesis of ⁴He below the equation. This is always dominant source of energy in stars that are larger than our sun.
¹²₆C + ₁¹H → ¹³₇N + γ 1.95 Mev...... (17)
¹³₇ N →¹³₆C + ₁⁰+ v 2.22 MeV......(18)
₆¹³ C + ¹₁→ ₇¹⁴+ γ 7.54MeV........(19)
₇¹⁴N + ¹₁H →₈¹⁵O + γ. 7.35MeV......(20)
₈¹⁵O → ₇¹⁵N + ₁⁰e+ v 2.75MeV .......(21) ₇¹⁵N+ ¹₁→ ₂⁴He + ₆¹²C 4.96 MeV......(22) 4 ₁¹H→ ₂⁴He + 2⁰₁+ 2v + 3γ 26.77MeV.... (23)
This more massive stars that consumed their helium and Hydrogen to make some of the richer chemical elements, these heavier atoms would get gravitate to the interior of the star creating even more dense and in the hottest environment.
The depending on the size of the stars helium atom burning could be followed by carbon burning and which is turn would be followed by the neon element burning and oxygen burning and silicon burning. Those all elements which the largest nuclear binding energies occurring for ferrous and nickel isotopes having mass number around within 56.
The fusion reaction leading to involving nucleus exothermic sustaining the life cycle of the star and preventing gravitational collapse.
All of the elements up to ⁵⁶ Ni undergoing two successive positron also emissions to produce ⁵⁶Fe can only formed in super massive stars as a result of nuclear fission following by neutron captured in the Red Super giant stars, which is having a life time of several millions years ago and heavier elements are actually formed gradually over the thousands of years by the s- process. The s-process increasingly S by a series of neutron captured following by the β- Decay. Two of the primary sources of the neutron used in the subsequent neutron capture derived from the collisions of α- particles with ¹³C and ²²Ne below the equation : (24) and (25)
¹³C + ⁴₂ He→ ₈¹⁶O+ ₀¹n......(24)
₁₀²²Ne + ⁴₂ He → ²⁵₁₂Mɡ + ₀¹n.....(25)
It's captured following by β- decay. Two of the main sources of the neutron used in the subsequent neutron captured derived from the collision of α- particles with ¹³C and ²²Ne (26)and (27)
¹³C + ⁴₂He → ₈¹⁶O + ₀¹n.......(26)
²²₁₀Ne+ ⁴₂He → ²⁵₁₂Mɡ + ₀¹n.....(27)
The example of the s-process can start with the any stable seed nucleus and each phase neutron capture occurs to increase A and then β- decay occurs whenever unstable nucleus is encountered. The largest isotopes can be produced by the s-process is ²⁰⁹Bi which is most heaviest stable nucleus on the band of stability.
The second type process by which nuclei heavier than ⁵⁶Fe can be formed known as the r-process. In many of the Red Super giants the stars eventually runs out of nuclear fuel and the core collapse under the influence of gravity, when it's happened it's very rapid process. Once the collapse reaches the certain critical nuclear density (~5×10¹⁴gram /cm³) any further collapse initiated a recoil the sars exploding as a supernova, emitting tremendous amount of energy and large burst of neutron and neutrinos. Under the extreme conditions of high neutron flux, neutron captured occurred on a fastest timescale than β- decay, so much heavier nuclei can be forming before the nucleus undergoes spontaneous β- decay, however a point is reached where the nuclear binding energy is so very small that the nucleus can no longer absorbed any more neutrons and the mass buildup is truncated. At this point the nucleus undergo a series of β- decay until a stable nuclide results. Example of the r-process below the equation,
¹¹⁶₄₈Cd+ 14₀¹n→ ₄₈¹³⁰cd →→→₅₂¹³⁰Te + 4_1⁰e..........(28)
Stars following a supernova depend on the exact point conditions. A neutron stars is very dense and extremely hot stars that is composed entirely of neutrinos and which is prevented undergoing further collapse by the "PAULI EXCLUSION PRINCIPLE", Which states that no two neutrons have the same exact quantum state. Because of a neutron star's enormous density, it has extremely large gravitational pull. The massive star's that center of the Crab nebula, whose extremely explosion was observed by the Chinese in 1054AD. The example of a rapidly rotating neutron starts known as a pulsar. A pulser emits electromagnetic radiation as it spin such that the light can only be observed when it faces the earth.
At the same manner as a rotating lighthouse works. A supernova explosion can also result in a " BLACK HOLE" In a black hole that gravitational fields of the objects at the core of the former stars is strongly that absolutely nothing not even light can escape from it's grasp.
In the life cycle of a star, the gaseous remnants results from a supernova explosive stream out into the cosmos forming the interstellar medium. Eventually some of the gases may coalesce under the influence of gravity to form a future - generation stars. Because the it's relativity young age only 4.7 billion years and presence of heavy nuclide such as Fe and it's core. Our sun is second or later generation stars. In fact the heavier elements found that on the earth crust, and either present in the interstellar dust as it aggregated together to form our solar system or deposited impact by the meteorites. Additionally many of the lighter elements such as Be, B, and Li, which are too unstable survive in the stellar nucleosynthesis, are believed to have been formed in the interstellar medium by the collision of more stable nuclei with galactic cosmic rays.
Lastly, all of the transuranium elements are don't exists naturally in the universe, were created by the laboratory using the high - energy collision of smaller nuclide that exist in nuclear reactors or in particle accelerators. It's a testament to the power of the human intellect and that we live in an age where it's possible synthesize elements that Nature herself couldn't create.
Example : How ¹⁹⁷Au (gold) can be created from ¹⁷⁵Lu ( Lutetium) using the r-process?
Solution : All the gold in the universe was originally created using the r-process in the supernova explosions.
¹⁷⁵₇₁Lu+ 22₀¹n→ ₇₁¹⁹⁷Lu→→→→→→→→₇₉¹⁹⁷Au+ 8_1⁰e
Good explanation
ReplyDeleteNice
ReplyDelete