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Regions of higher density collapsed more rapidly under gravity, eventually resulting in the large-scale, foam-like structure or "cosmic web" of voids and galaxy filaments seen today. Voids located in high-density environments are smaller than voids situated in low-density spaces of the universe. [3]
Size comparison of the event horizons of the black holes of TON 618 and Phoenix A.The orbit of Neptune (white oval) is included for comparison. As a quasar, TON 618 is believed to be the active galactic nucleus at the center of a galaxy, the engine of which is a supermassive black hole feeding on intensely hot gas and matter in an accretion disc.
Earth (0.98–1.02 AU) [D 6] is the only place in the universe where life and surface liquid water are known to exist. [102] Earth's atmosphere contains 78% nitrogen and 21% oxygen, which is the result of the presence of life. [103] [104] The planet has a complex climate and weather system, with conditions differing drastically between climate ...
The Solar System is located within a structure called the Local Bubble, a low-density region of the galactic interstellar medium. [5] Within this region is the Local Interstellar Cloud (LIC), an area of slightly higher hydrogen density. It is estimated that the Solar System entered the LIC within the past 10,000 years. [6]
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.
The density of dark matter in an expanding universe decreases more quickly than dark energy, and eventually the dark energy dominates. Specifically, when the volume of the universe doubles, the density of dark matter is halved, but the density of dark energy is nearly unchanged (it is exactly constant in the case of a cosmological constant).
For years, scientists have been troubled by an unusual feature of our universe. It appears to be expanding faster today than it did in the past – and researchers are not sure why.
The diffuse photoionized gas contains filaments of higher density, about one atom per cubic meter, [145] which is 5–200 times the average density of the universe. [146] The IGM is inferred to be mostly primordial in composition, with 76% hydrogen by mass, and enriched with higher mass elements from high-velocity galactic outflows. [147]