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The comoving distance from Earth to the edge of the observable universe is about 14.26 gigaparsecs (46.5 billion light-years or 4.40 × 10 26 m) in any direction. The observable universe is thus a sphere with a diameter of about 28.5 gigaparsecs [27] (93 billion light-years or 8.8 × 10 26 m). [28]
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 ...
The observable universe contains as many as an estimated 2 trillion galaxies [95] [96] [97] and, overall, as many as an estimated 10 24 stars [98] [99] – more stars (and earth-like planets) than all the grains of beach sand on planet Earth; [100] [101] [102] but less than the total number of atoms estimated in the universe as 10 82; [103] and ...
For comparisons with the light travel distance of the astronomical objects listed below, the age of the universe since the Big Bang is currently estimated as 13.787±0.020 Gyr. [1] Distances to remote objects, other than those in nearby galaxies, are nearly always inferred by measuring the cosmological redshift of their light. By their nature ...
Hence, it is unclear whether the observable universe matches the entire universe or is significantly smaller, though it is generally accepted that the universe is larger than the observable universe. The universe may be compact in some dimensions and not in others, similar to how a cuboid [citation needed] is longer in one dimension than the ...
The Hubble eXtreme Deep Field (XDF) was completed in September 2012 and shows the farthest galaxies ever photographed at that time. Except for the few stars in the foreground (which are bright and easily recognizable because only they have diffraction spikes), every speck of light in the photo is an individual galaxy, some of them as old as 13.2 billion years; the observable universe is ...
In astrophysics, the term "cosmography" is beginning to be used to describe attempts to determine the large-scale matter distribution and kinematics of the observable universe, dependent on the Friedmann–Lemaître–Robertson–Walker metric but independent of the temporal dependence of the scale factor on the matter/energy composition of the Universe.
Rather, the conformal time is the amount of time it would take a photon to travel from where we are located to the furthest observable distance, provided the universe ceased expanding. As such, η 0 {\displaystyle \eta _{0}} is not a physically meaningful time (this much time has not yet actually passed); though, as we will see, the particle ...