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What is the critical temperature at which hydrogen can begin to fuse into helium in the core of a star?
Wiki User
∙ 14y ago
Helium fusion occurs in the core of the stars that are in that stage of life where they have exhausted their hydrogen fuel and begin to burn helium. Wikipedia has some additional information and a link is provided.
Wiki User
∙ 15y ago
Wiki User
∙ 8y agoStellar nucleosynthesis (nuclear fusion) began in our sun about 5 billion years ago. For about a million years prior to nuclear ignition our sun shined by Helmholtz Contraction, essentially light and heat emitted from gradual gravitational condensation of gas collapsing onto the nascent star's surface. At that time our sun was part of a loose cluster of stars in a big cloud or nebula of gas stretching light years across.
Wiki User
∙ 14y agoIn the Sun, almost all of the fusion energy is released by the fusion of hydrogen into helium. The process, which requires high density and temperature, produces energy through the loss of mass. Through a three-step process (each creating energy), a pair of hydrogen atoms combine to form a single helium atom.
This is called the proton-proton chain reaction.
The first stage involves the combination of two separate atoms of hydrogen into deuterium, an isotope having one proton and one neutron in its nucleus, instead of just a proton. Energy is released when one proton forms a neutron, a neutrino, and a positron. More energy is released when the positron annihilates with an electron.
In the second stage, the deuterium atom combines with a single-proton hydrogen atom to form a single-neutron isotope of helium (helium-3). This also releases energy.
In the most common third stage, two of these helium-3 atoms fuse to form a single atom of helium-4, the common form of helium, throwing off the two extra protons as hydrogen nuclei.
(Other reactions can temporarily form beryllium or lithium, which decay to form helium.)
The final mass of the helium atoms is slightly less than the mass of the hydrogen from which it was formed. This missing mass has been converted into energy, in the form of gamma ray photons and neutrinos. The photons' energy is transferred to the surrounding matter and moves outward from the core to the Sun's surface, where it is emitted as solar radiation.
(The neutrinos, however, easily pass through the Sun and escape into space at nearly the speed of light. They also pass through the Earth and other planets, where only a tiny fraction ever collide with an atom.)
Wiki User
∙ 12y agoUsually in the core, where the temperature and the pressure are the greatest. Sometimes also on a star's surface, if a lot of mass - usually from another star in the same star system - falls onto the surface.
Wiki User
∙ 12y agoHydrogen fusion occurs in the core of the Sun. The core of the Sun is hotter than any other place on the Sun due to the heat produced from the fusion and the gravitational force. The Sun also has a conducive density for fusion.
Wiki User
∙ 6y agoit happens in the core (center) of the sun (nuclear fusion happens only at high temperature and pressure).
Wiki User
∙ 14y agoWhen the core temperature reaches about 10 million kelvin, this will initiate the proton-proton chain reaction allowing hydrogen to fuse into helium.
Wiki User
∙ 12y agoIn our sun, deep in the core. In larger stars fusion may occur in a shell around the core.
Wiki User
∙ 13y ago15,000,000 K (26,999,540.3 degrees Fahrenheit)
Wiki User
∙ 6y agoEssentially fusion of hydrogen nuclei, which means protons. Sometimes it is called the proton-proton reaction
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How is a star able to begin helium fusion after it ran out of hydrogen?
The basic idea is that once a star runs out of hydrogen fuel, it starts contracting until it gets hot enough to fuse helium into heavier elements. This happens at temperatures that are quite a bit higher than the temperatures required to fuse hydrogen into helium.
A star that has exhausted it's supply of hydrogen?
It will begin to swell and may start it's red giant phase. The stars preferred fuel is hydrogen, but once this had been used it will start to fuse helium. The temperature of the core will rise and the output energy and gravity battle will shift, causing the star to become larger.
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.
Where is your sun in its life cycle?
The sun is in its middle age. Its around 5 billion years old, and will keep fusing hydrogen into helium for another 5 billion years. In about 5 billion years the sun's core will run out of Hydrogen and begin fusing helium into carbon. At this point the sun will balloon outwards become 1 to 10 times its current size but the surface temperature will lower because it is further from the core. It will turn red in color and eventually after it has fused all the helium into carbon it will release its out layers into what is known as a planetary nebula and nothing will be left but the white hot core known as a white dwarf star.
What are the main elements that make up a star?
For main sequence stars, the vast majority is hydrogen and helium. Older stars will exhaust these lighter elements near their cores and begin fusing heavier elements.
When does helium fusion begin in a star?
Hydrogen undergoes nuclear fusion to form helium at a temperature of 107 K
When does hydrogen first begin to fuse into helium in the star formation process?
When the temperature of the core reaches 10 billion degrees kelvin
What are science words that begin with letter h?
Hydrogen, hafnium, helium, holmium and hassium are chemical elements.
How is a star able to begin helium fusion after it ran out of hydrogen?
The basic idea is that once a star runs out of hydrogen fuel, it starts contracting until it gets hot enough to fuse helium into heavier elements. This happens at temperatures that are quite a bit higher than the temperatures required to fuse hydrogen into helium.
Some scientific words that start with an H?
Halogen, Helium and hydrogen are science words. They begin with the letter H.
What heavier element is created when hydrogen atoms fuse together in the suns core?
Normal "main sequence" stars fuse hydrogen into helium during most of the star's life. The core of a star gets so hot that the hydrogen atoms begin to fuse together. As hydrogen only has 1 proton when if fuses with another hydrogen atom it has 2 protons so has become helium.
A star that has exhausted it's supply of hydrogen?
It will begin to swell and may start it's red giant phase. The stars preferred fuel is hydrogen, but once this had been used it will start to fuse helium. The temperature of the core will rise and the output energy and gravity battle will shift, causing the star to become larger.
What gas makes up the majority of an old star?
Even in an old star just before it explodes, the majority of the star in hydrogen gas. But as the hydrogen is fused, the helium residue begins to interfere with the hydrogen fusion, like ashes in the bottom of a fireplace.
How does the amount of Hydrogen differ from that of helium in the Sun mass?
The Sun is about 70% hydrogen, 28% helium, and 2% "other". When the Sun gets to about 50% hydrogen, the amount of helium present will seriously interfere with the hydrogen fusion, and the Sun will begin to collapse under its own gravity. The Sun's core is currently around 15 million degrees Kelvin. As the Sun collapses, the increasing pressure will heat the Sun, and when it gets to about 45 million degrees, the Sun will begin fusing helium and with the new power source will expand into a red giant. We expect this to happen in about 4 billion years, perhaps a little more.
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.
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.
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.
