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The first one, the proton–proton chain reaction, is the dominant energy source in stars with masses up to about the mass of the Sun. The second process, the carbon–nitrogen–oxygen cycle, which was also considered by Carl Friedrich von Weizsäcker in 1938, is more important in more massive main-sequence stars.
Nitrogen is a chemical element; it has symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh in total abundance in the Milky Way and the Solar System.
The problem was that while the concentration of deuterium in the universe is consistent with the Big Bang model as a whole, it is too high to be consistent with a model that presumes that most of the universe is composed of protons and neutrons. If one assumes that all of the universe consists of protons and neutrons, the density of the ...
The universe has appeared much the same as it does now, for many billions of years. It will continue to look similar for many more billions of years into the future. The galactic disk of the Milky Way is estimated to have been formed 8.8 ± 1.7 billion years ago but only the age of the Sun, 4.567 billion years, is known precisely. [81]
The hydrogen and most of the helium in the Sun would have been produced by Big Bang nucleosynthesis in the first 20 minutes of the universe, and the heavier elements were produced by previous generations of stars before the Sun was formed, and spread into the interstellar medium during the final stages of stellar life and by events such as ...
Astronomers have discovered what may be the brightest object in the universe, a quasar with a black hole at its heart growing so fast that it swallows the equivalent of a sun a day. The black hole ...
All-sky map of the CMB, created from nine years of WMAP data. c. 370,000 years (z = 1,100): The "Dark Ages" is the period between decoupling, when the universe first becomes transparent, until the formation of the first stars. Recombination: electrons combine with nuclei to form atoms, mostly hydrogen and helium. Ordinary matter particles ...
New Year's Day saw the Northern Lights dazzle across North Yorkshire skies in the first display of 2025. BBC Weather Watchers in areas including York, Skipton and Malton captured the pink, purple ...