Nucleosynthesis helium

This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. March Learn how and when to remove this template message Deuterium is in some ways the opposite of helium-4, in that while helium-4 is very stable and difficult to destroy, deuterium is only marginally stable and easy to destroy.

Nucleosynthesis helium

It is now known that the elements observed in the Universe were created in either of two ways. Light elements namely deuterium, helium, and lithium were produced in the first few minutes of the Big Bang, while elements heavier than helium are thought to have their origins in the interiors of stars which formed much later in the history of the Universe.

Both theory and observation lead astronomers to believe this to be the case. Burbidge, Fowler, and Hoyle. The BBFH theory, as it came to be known, postulated that all the elements were produced either in stellar interiors or during supernova explosions.

While this theory achieved relative success, it was discovered to be lacking in some important respects. To begin with, it was estimated that only a small amount of matter found in the Universe should consist of helium if stellar nuclear reactions were its only source of production.

A similar enigma exists for the deuterium. According to stellar theory, deuterium cannot be produced in stellar interiors; actually, deuterium is destroyed inside of stars. Hence, the BBFH hypothesis could not by itself adequately explain the observed abundances of helium and deuterium in the Universe.

Thanks to the pioneering efforts of George Gamow and his collaborators, there now exists a satisfactory theory as to the production of light elements in the early Universe. In the very early Universe the temperature was so great that all matter was fully ionized and dissociated.

At this temperature, nucleosynthesis, or the production of light elements, could take place. In a short time interval, protons and neutrons collided to produce deuterium one proton bound to one neutron. Most of the deuterium then collided with other protons and neutrons to produce helium and a small amount of tritium one proton and two neutrons.

Lithium 7 could also arise form the coalescence of one tritium and two deuterium nuclei. It also predicts about 0. The important point is that the prediction depends critically on the density of baryons ie neutrons and protons at the time of nucleosynthesis.

Furthermore, one value of this baryon density can explain all the abundances at once. In terms of the present day critical density of matter, the required density of baryons is a few percent the exact value depends on the assumed value of the Hubble constant.

This relatively low value means that not all of the dark matter can be baryonic, ie we are forced to consider more exotic particle candidates.

Nucleosynthesis helium

This is one of the corner-stones of the Hot Big Bang model. Further support comes from the consistency of the other light element abundances for one particular baryon density and an independent measurement of the baryon density from the anisotropies in the cosmic microwave background radiation.

It seems like we really understand the physical processes which went on in the first few minutes of the evolution of the Universe! Further details can be found here.The Big Bang Nucleosynthesis theory predicts that roughly 25% the mass of the Universe consists of Helium.

It also predicts about % deuterium, and even smaller quantities of lithium. The important point is that the prediction depends critically on the density of baryons (ie neutrons and protons) at the time of nucleosynthesis.

Big Bang Nucleosynthesis The modeling of the early universe by the standard big bang model gives a scenario that involves twelve nuclear interactions that led to the present cosmic abundances of elements outside the stars.

The vast majority of the mass of ordinary matter in the universe is hydrogen and helium, remaining from the early stages of the universe. Primordial nucleosynthesis is believed by most cosmologists to have taken place in the interval from roughly 10 seconds to 20 minutes after the Big Bang, and is calculated to be responsible for the formation of most of the universe's helium as the isotope helium-4 (4 He), along with small amounts of the hydrogen isotope deuterium (2 H or D), the helium isotope helium-3 (3 He), and a very small .

After the hydrogen in the star's core is exhausted, the star can burn helium to form progressively heavier elements, carbon and oxygen and so on, until iron and nickel are .

Big Bang Nucleosynthesis The Universe's light-element abundance is another important criterion by which the Big Bang hypothesis is verified. It is now known that the elements observed in the Universe were created in either of two ways. Light elements (namely deuterium, helium, and lithium) were produced in the first few minutes of the Big Bang.

big bang nucleosynthesis. By the first millisecond, the universe had cooled to a few trillion kelvins Yet, hydrogen and helium together won't make anything as complex and as interesting as the Earth, or a bacterium, or a refrigerator, or you and I.

To do that we need carbon and oxygen and nitrogen and silicon and chlorine and every other.

Nucleosynthesis - Wikipedia