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This serves as a working definition even though there is no single agreed-upon definition of what constitutes a void. The matter density value used for describing the cosmic mean density is usually based on a ratio of the number of galaxies per unit volume rather than the total mass of the matter contained in a unit volume. [9]
But the total radiation emitted by a star (or other cosmic object) is at most equal to the total nuclear binding energy of isotopes in the star. For the density of the observable universe of about 4.6×10 −28 kg/m 3 and given the known abundance of the chemical elements, the corresponding maximal radiation energy density of 9.2×10 −31 kg/m ...
A type of naturally occurring physical entity, association, or structure that exists within the observable universe but is a more complex, less cohesively bound structure than an astronomical body, consisting perhaps of multiple bodies or even other objects with substructures, such as a planetary system, star cluster, nebula, or galaxy. Though ...
Bentley's paradox: In a Newtonian universe, gravitation should pull all matter into a single point. Boltzmann brain: If the universe we observe resulted from a random thermodynamic fluctuation, it would be vastly more likely to be a simple one than the complex one we observe. The simplest case would be just a brain floating in vacuum, having ...
A quasi-star (also called black hole star) is a hypothetical type of extremely large and luminous star that may have existed early in the history of the Universe. They are thought to have existed for around 7–10 million years due to their immense mass .
A final state for a star in the far future (10 1500 years) of the universe, when all matter is transmuted to iron via quantum tunneling. — The universe isn't old enough for this form to come into existence. MECO: A hypothetical alternative to black holes. Q0957+561: Planck star: A star where the energy density is around the Planck density.
"The unusual object, called CX330, was first detected as a source of X-ray light in 2009," according to a NASA news press release. It's closest neighboring star formation is over a thousand light ...
[5] [6] [7] As the density further increases, the remaining electrons react with the protons to form more neutrons. The collapse continues until (at higher density) the neutrons become degenerate. A new equilibrium is possible after the star shrinks by three orders of magnitude, to a radius between 10 and 20 km. This is a neutron star.