Search results
Results From The WOW.Com Content Network
Stars fuse light elements to heavier ones in their cores, giving off energy in the process known as stellar nucleosynthesis. Nuclear fusion reactions create many of the lighter elements, up to and including iron and nickel in the most massive stars. Products of stellar nucleosynthesis remain trapped in stellar cores and remnants except if ...
Almost all neutrons that fused instead of decaying ended up combined into helium-4, due to the fact that helium-4 has the highest binding energy per nucleon among light elements. This predicts that about 8% of all atoms should be helium-4, leading to a mass fraction of helium-4 of about 25%, which is in line with observations.
Free protons of high energy and velocity make up 90% of cosmic rays, which propagate through the interstellar medium. [33] Free protons are emitted directly from atomic nuclei in some rare types of radioactive decay. [34] Protons also result (along with electrons and antineutrinos) from the radioactive decay of free neutrons, which are unstable ...
Close to the end of this epoch, only light-stable baryons (protons and neutrons) remain. Due to the sufficiently high density of leptons, protons and neutrons rapidly change into one another under the action of weak force. Due to the higher mass of neutron the neutron:proton ratio, which is initially 1:1, starts to decrease. Neutrino decoupling ...
Helium, for instance, was thought to have four protons and two nuclear electrons in the nucleus, leaving two excess protons and a net nuclear charge of 2+. After the neutron was discovered, scientists realized the helium nucleus in fact contained two protons and two neutrons.
However, this does not by itself significantly alter the abundances of elements in the universe as the elements are contained within the star. Later in its life, a low-mass star will slowly eject its atmosphere via stellar wind, forming a planetary nebula, while a higher–mass star will eject mass via a sudden catastrophic event called a supernova
Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun , from outside of the Solar System in our own galaxy, [ 1 ] and from distant galaxies. [ 2 ]
[4] [5] Like all nuclei, preceding the discovery of the neutron, it is assumed to be composed entirely of protons and hypothetical "nuclear electrons". On February 27, James Chadwick publishes the discovery of the neutron , identified as the "beryllium radiation" emitted under alpha-particle bombardment, previously observed by Irène Joliot ...