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  2. Observable universe - Wikipedia

    en.wikipedia.org/wiki/Observable_universe

    The radius of the observable universe is therefore estimated to be about 46.5 billion light-years. [8] [9] Using the critical density and the diameter of the observable universe, the total mass of ordinary matter in the universe can be calculated to be about 1.5 × 10 53 kg. [10]

  3. Orders of magnitude (length) - Wikipedia

    en.wikipedia.org/wiki/Orders_of_magnitude_(length)

    886.48 Ym – 93.7 billion light-years – the diameter of the observable universe (twice the particle horizon); however, there might be unobserved distances that are even greater. 1 ronnameter The ronnametre ( SI symbol: Rm ) is a unit of length in the metric system equal to 10 27 meters .

  4. Cosmological horizon - Wikipedia

    en.wikipedia.org/wiki/Cosmological_horizon

    It represents the boundary between the observable and the unobservable regions of the universe, so its distance at the present epoch defines the size of the observable universe. Due to the expansion of the universe, it is not simply the age of the universe times the speed of light, as in the Hubble horizon, but rather the speed of light ...

  5. Shape of the universe - Wikipedia

    en.wikipedia.org/wiki/Shape_of_the_universe

    A finite universe is a bounded metric space, where there is some distance d such that all points are within distance d of each other. The smallest such d is called the diameter of the universe, in which case the universe has a well-defined "volume" or "scale".

  6. Universe - Wikipedia

    en.wikipedia.org/wiki/Universe

    The physical universe is defined as all of space and time [a] (collectively referred to as spacetime) and their contents. [10] Such contents comprise all of energy in its various forms, including electromagnetic radiation and matter, and therefore planets, moons, stars, galaxies, and the contents of intergalactic space.

  7. List of largest cosmic structures - Wikipedia

    en.wikipedia.org/wiki/List_of_largest_cosmic...

    Discovered through gamma-ray burst mapping. Largest-known regular formation in the observable universe. [8] Huge-LQG (2012–2013) 4,000,000,000 [9] [10] [11] Decoupling of 73 quasars. Largest-known large quasar group and the first structure found to exceed 3 billion light-years. "Giant Arc" (2021) 3,300,000,000 [12] Located 9.2 billion light ...

  8. Angular diameter - Wikipedia

    en.wikipedia.org/wiki/Angular_diameter

    an object of diameter 1 AU (149 597 871 km) at a distance of 1 parsec (pc) Thus, the angular diameter of Earth's orbit around the Sun as viewed from a distance of 1 pc is 2″, as 1 AU is the mean radius of Earth's orbit. The angular diameter of the Sun, from a distance of one light-year, is 0.03″, and that of Earth 0.0003″. The angular ...

  9. Galaxy - Wikipedia

    en.wikipedia.org/wiki/Galaxy

    The isophotal diameter is introduced as a conventional way of measuring a galaxy's size based on its apparent surface brightness. [139] Isophotes are curves in a diagram - such as a picture of a galaxy - that adjoins points of equal brightnesses, and are useful in defining the extent of the galaxy.