Search results
Results from the WOW.Com Content Network
The observable universe contains as many as an estimated 2 trillion galaxies [36] [37] [38] and, overall, as many as an estimated 10 24 stars [39] [40] – more stars (and, potentially, Earth-like planets) than all the grains of beach sand on planet Earth. [41] [42] [43] Other estimates are in the hundreds of billions rather than trillions.
What happens after a low-mass star ceases to produce energy through fusion has not been directly observed; the universe is around 13.8 billion years old, which is less time (by several orders of magnitude, in some cases) than it takes for fusion to cease in such stars.
12 C, a stable isotope of carbon, is abundantly produced in stars due to three factors: The decay lifetime of a 8 Be nucleus is four orders of magnitude larger than the time for two 4 He nuclei (alpha particles) to scatter. [18] An excited state of the 12 C nucleus exists a little (0.3193 MeV) above the energy level of 8 Be + 4 He.
The observable universe contains as many as an estimated 2 trillion galaxies [95] [96] [97] and, overall, as many as an estimated 10 24 stars [98] [99] – more stars (and earth-like planets) than all the grains of beach sand on planet Earth; [100] [101] [102] but less than the total number of atoms estimated in the universe as 10 82; [103] and ...
The images show the surface of the star R. Doradus, a red giant star 180 light-years away in the Dorado constellation. The star has a diameter about 350 times that of the sun, and it serves as a ...
This core convection occurs in stars where the CNO cycle contributes more than 20% of the total energy. As the star ages and the core temperature increases, the region occupied by the convection zone slowly shrinks from 20% of the mass down to the inner 8% of the mass. [25] The Sun produces on the order of 1% of its energy from the CNO cycle.
During a star's evolution, convective mixing episodes moves material, within which the CNO cycle has operated, from the star's interior to the surface, altering the observed composition of the star. Red giant stars are observed to have lower carbon-12/carbon-13 and carbon-12/nitrogen-14 ratios than do main sequence stars, which is considered to ...
Once stars begin to form, emit radiation, and in some cases explode, the process of galaxy formation becomes very complex, involving interactions between the forces of gravity, radiation, and thermal energy. Many details are still poorly understood. [192] Within a billion years of a galaxy's formation, key structures begin to appear. [193]