What is the Radiative Zone?
A radiation zone is a layer in the interior of a star where energy is transported outwards by radiative diffusion and thermal conduction rather than by convection.
The opacity and radiation flux within a star’s layers determine how effective radiative diffusion is at transporting energy. High opacity or high luminosity causes a high-temperature gradient.
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The radiation zone is stable against the formation of convection cells if the density gradient is high enough.
A polytrope solution with n=3 and a left-hand side constant gives a stable radiation zone against convection.
At a sufficiently large radius, the opacity increases due to the decrease in temperature and possibly also due to a lower degree of ionization in the lower shells of the heavy element ions.
Main sequence stars are entirely convective below 0.3 solar masses and have a radiative zone around the stellar core. Above 1.2 solar masses, the radiative zone becomes a convection zone.
The radiation zone is a region of the Sun between the solar core and the outer convection zone.
The radiation zone is a thick layer of highly ionized, very dense gases that are constantly bombarded by the gamma rays of the nucleus. It consists of about 75% hydrogen and 24% helium. Since most of the atoms here lack electrons, they cannot absorb photons that might penetrate the surface. Most photons simply bounce back. Occasionally, a photon is absorbed.
When the Sun cools from a fusion fireball to a plasma ball, it happens at the interface between the radiation zone and the radiation zone. No convection occurs in this layer, he said. Instead, heat is transferred via thermal radiation. The incoming light particles (photons) are absorbed in specific ways by specific atoms inside the star before being transmitted back at higher frequencies. It can take light particles thousands of years to spiral through this layer before they finally reach the star’s surface.
What is the Sun’s nuclear fusion?
Because all other protons repel all other protons, the average proton must collide head-on with another proton and be fast enough to merge in 7 billion years. In the Sun, there are many protons, so some collide in seconds, and others never will. This is why the sun doesn’t explode all at once. Due to the instability of the two-proton nucleus, one of the protons decays into a neutron right away. Neutrinos and positrons are released during the decay. As the positron collides with the electron (the antimatter equivalent of the electron), both become gamma rays. After leaving the sun, neutrinos travel at nearly the speed of light.
What is the difference between a nucleus and an atomic nucleus?
These two collide, forming for a moment a sphere with four protons and two neutrons. But two protons are knocked away by the force of the collision, leaving a stable helium nucleus with two protons and two neutrons.
What is the Sun’s origin?
Five billion years ago, the Sun’s predecessor was a cloud with a diameter of 500 trillion kilometers or 50 light years. It was a near vacuum.
What Happens When a Cloud collapses?
These globules were still what Earth would consider a vacuum, and their temperatures had only risen to -400° F (-240° C). They were visible only as dark circles beneath a blanket of dust, and each orb was a trillion miles across and 25 solar masses in mass.
What was the Sun’s diameter?
After a few more thousand years, our sun had a diameter of about 225 million miles. The temperature in the core often exceeded 60 000 °C, which is hot enough to remove the electrons from the atoms, but not yet hot enough to melt two hydrogen nuclei. The surface temperature was about 1500 °C, cooler than the Sun’s surface today, but large enough to emit many times more light than the Sun.
What Happens When the Sun collapses?
After five billion years, fusion in the Sun’s core will cease and gravity will cause the star to collapse. The heat of the collapse will exceed the heat of fusion; it will even reach 150 000 000 000° F (about 80 000 000 000° C), and the Sun will expand for a few hundred million years, eventually swallowing up the planet Mercury. As the Sun grows, it will become a red giant. Then its surface will be so large that it will emit 500 times more light than it does today.
What happens when it produces too much heat?
The core will then be hot enough to melt helium into carbon and oxygen. Fusion will generate more heat, so much so that the new helium-rich nucleus can no longer radiate. In a few hours, the core will explode. The Sun’s outer layer absorbs the explosion. The core will lose enough heat to stabilize and begin to collapse. Again it will produce too much heat and explode, causing the Sun to swell dramatically. This process will repeat, so the Sun will grow and shrink many times.
What is the core of the sun made of?
The core of the Sun is made up of 64% helium, surrounded by a shell of molten hydrogen – 35% of the core’s mass. All the other elements in the Universe make up only 1% of the Sun’s core. All the energy the Sun radiates is generated in the core. The energy generated every second by 4.5 million tonnes of matter in the core raises its temperature to a spectacular 14 000 000 °C.
The nuclear reaction that takes place in the nucleus produces tiny particles called neutrinos that react surprisingly little with matter. These particles rush out of the Sun at almost the speed of light and take just five seconds to do so. The energy produced by this reaction is emitted in the form of gamma rays.
Due to the density of the Sun’s core – 10 times denser than silver or iron – and the state of the atoms in the core, photons can’t get sucked back in. Before leaving the core, they bounce around for 40 million years.
