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Simulated collision of two neutron stars. A stellar collision is the coming together of two stars [1] caused by stellar dynamics within a star cluster, or by the orbital decay of a binary star due to stellar mass loss or gravitational radiation, or by other mechanisms not yet well understood.
17 August 2017: Gravitational wave detected from merger of two neutron stars (00:23 video; artist concept). On 17 August 2017, the LIGO and Virgo interferometers observed GW170817, [7] a gravitational wave associated with the merger of a binary neutron star (BNS) system in NGC 4993, an elliptical galaxy in the constellation Hydra about 140 million light years away. [8]
Representative lifetimes of stars as a function of their masses The change in size with time of a Sun-like star Artist's depiction of the life cycle of a Sun-like star, starting as a main-sequence star at lower left then expanding through the subgiant and giant phases, until its outer envelope is expelled to form a planetary nebula at upper right Chart of stellar evolution A mass-radius plot ...
This final burning in massive stars, called explosive nucleosynthesis or supernova nucleosynthesis, is the final epoch of stellar nucleosynthesis. A stimulus to the development of the theory of nucleosynthesis was the discovery of variations in the abundances of elements found in the universe .
The s-process is believed to occur mostly in asymptotic giant branch stars, seeded by iron nuclei left by a supernova during a previous generation of stars. In contrast to the r-process which is believed to occur over time scales of seconds in explosive environments, the s-process is believed to occur over time scales of thousands of years, passing decades between neutron captures.
Gravitational collapse is a fundamental mechanism for structure formation in the universe. Over time an initial, relatively smooth distribution of matter , after sufficient accretion , may collapse to form pockets of higher density, such as stars or black holes .
Atherosclerosis: Overview. This article was reviewed by Craig Primack, MD, FACP, FAAP, FOMA. Atherosclerosis happens when a fatty substance called plaque builds up inside your arteries.
In the dense nebulae where stars are produced, much of the hydrogen is in the molecular (H 2) form, so these nebulae are called molecular clouds. [4] The Herschel Space Observatory has revealed that filaments, or elongated dense gas structures, are truly ubiquitous in molecular clouds and central to the star formation process. They fragment ...