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Which nuclear fusion cycle is the next one to begin after helium fusion ends in a massive star?
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When does helium fusion begin in a star?
Hydrogen undergoes nuclear fusion to form helium at a temperature of 107 K
When will helium fusion begin?
5 min
How does nuclear fusion occur in the Sun?
At this time hydrogen to helium burning. 1H + 1H --> 2H + e + ~1 MeV 2H + 2H --> 3H + 1H + ~4 MeV 2H + 3H --> 4He + n + ~17 MeV and several other side reactions. When it runs out of hydrogen, the core will begin helium burning. This is much harder to start so it requires much higher pressure and temperature. 3 4He --> 12C But this will not begin for another 6 billion years.
At what temperature do star begin the process of nuclear fusion?
Between 10 and 15 million degrees.
When does nuclear fusion begin?
First deuterium and tritium (hydrogen isotopes) are put in. Next they are compressed using many super electromagnets, producing heat, that fuses them together, making radioactive helium. Then the extra proton fall off, making stable helium.
When does helium fusion begin in a star?
Hydrogen undergoes nuclear fusion to form helium at a temperature of 107 K
When will helium fusion begin?
5 min
A protostar becomes a star when?
A star is born when contracting gas and dust from a nebula become so dense and hot that nuclear fusion starts.
What triggers nuclear fusion stars?
Fusion in stars are usually the result of gravity.Once a mass of hydrogen accumulates enough mass, the gravity of all that mass compresses the core of the star to the point that the hydrogen atoms there begin fusing into helium. The process then cascades outward, and the end result is a star.
How does nuclear fusion occur in the Sun?
At this time hydrogen to helium burning. 1H + 1H --> 2H + e + ~1 MeV 2H + 2H --> 3H + 1H + ~4 MeV 2H + 3H --> 4He + n + ~17 MeV and several other side reactions. When it runs out of hydrogen, the core will begin helium burning. This is much harder to start so it requires much higher pressure and temperature. 3 4He --> 12C But this will not begin for another 6 billion years.
At what temperature do star begin the process of nuclear fusion?
Between 10 and 15 million degrees.
When does nuclear fusion begin?
First deuterium and tritium (hydrogen isotopes) are put in. Next they are compressed using many super electromagnets, producing heat, that fuses them together, making radioactive helium. Then the extra proton fall off, making stable helium.
Inside a prostar the nuclear fusion of hydrogen will begin when?
The core of the protostar reached an extremely high temperature
How many years does it take a star with mass of the sun to convert its hydrogen to its core?
No star will EVER convert ALL of the hydrogen to helium via nuclear fusion (the process that powers the star) because when the star is less than about 50% hydrogen, the helium gets in the way of the fusion reaction and the star begins to die out. The star will begin to shrink as the star's own gravity now is more powerful than the nuclear reaction, and the star will get more dense and will heat up. If the internal temperature and pressure gets high enough, the star will begin fusing helium into even heavier elements, becoming a red giant. The speed of this reaction depends on the original mass of the star.
Why don't all stars end their life the same way?
Not at all. The end state of a star depends almost entirely on the beginning mass of the star. Small stars like red dwarf stars will continue essentially forever. They will continue to fuse their supply of hydrogen until the helium "ash" begins to inhibit hydrogen fusion, and will begin to cool very slowly. They will never get hot enough to begin helium fusion, but the expected lifetime is longer than the age of the universe. More massive stars like the Sun will fuse their hydrogen until helium begins to inhibit the hydrogen fusion, and they will begin to collapse. This increases the temperature and pressure until they begin to fuse helium, at which time the star will expand into red giant, in about 4 billion years. Very massive stars will fuse their hydrogen, and then helium, until they explode in nova or supernova explosions. The end result would be either a neutron star or a black hole, depending on the initial mass. The more massive the star, the faster it burns out. A supergiant star like Betelgeuse is already old at only 100 million years or so, and will probably go supernova "soon". However, "soon" to an astronomer could be anywhere in the next 10,000 years.
Why do protostars reach a stage at which they stop contracting?
Eventually, when the star becomes sufficiently massive, the pressure in the core sends temperatures high enough to begin nuclear fusion, and gravity (which so far has been the dominant force) is counterbalanced by radiation pressure.
Does fusion occur when hydrogen atoms join together?
Helium fusion is a process that happens as a part of what is called stellar nucleosynthesis. That's a term we apply to the mechanisms working within stars. Stars are fusion engines, and they are powered primarily by fusing the element hydrogen into the element helium (the first and second most abundant elements in the universe, respectively). This process sometimes goes under the name proton-proton reaction. As stars exhaust their hydrogen fuel and build up a lot of helium, they begin to fuse the helium together to form the element carbon in what is called the triple-alpha process. Links are provided to the relevant Wikipedia articles. Our friends there provide knowledge for free.
