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It forms a slightly brighter elliptical spot of 8–10° across directly opposite the Sun within the dimmer band of zodiacal light and zodiac constellation. [2] The intensity of the gegenschein is relatively enhanced because each dust particle is seen at full phase , [ 3 ] having a difficult to measure apparent magnitude of +5 to +6, with a ...
A terrestrial planet that is more habitable than Earth. Tidally detached exomoon: A planet that was originally a moon but has become gravitationally detached. Toroidal planet: A planet whose shape resembles a torus or doughnut. Trojan planet: A planet that orbits near the L 4 or L 5 Lagrange points of a more massive object.
The accretion of gas stops when the supply from the disk is exhausted. [67] This happens gradually, due to the formation of a density gap in the protoplanetary disk and to disk dispersal. [34] [72] In this model ice giants—Uranus and Neptune—are failed cores that began gas accretion too late, when almost all gas had already disappeared.
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 ...
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]
The universe can be viewed as having a hierarchical structure. [2] At the largest scales, the fundamental component of assembly is the galaxy. Galaxies are organized into groups and clusters, often within larger superclusters, that are strung along great filaments between nearly empty voids, forming a web that spans the observable universe. [3]
Assuming the universe is isotropic, the distance to the edge of the observable universe is roughly the same in every direction. That is, the observable universe is a spherical region centered on the observer. Every location in the universe has its own observable universe, which may or may not overlap with the one centered on Earth.
After about 9.8 billion years, the universe had expanded sufficiently so that the density of matter was less than the density of dark energy, marking the beginning of the present dark-energy-dominated era. [45] In this era, the expansion of the universe is accelerating due to dark energy.