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The Hubble volume is approximately equal to 10 31 cubic light years (or about 10 79 cubic meters). The proper radius of a Hubble sphere (known as the Hubble radius or the Hubble length) is /, where is the speed of light and is the Hubble constant. The surface of a Hubble sphere is called the microphysical horizon, [2] the Hubble surface, or the ...
Hubble radius, Hubble sphere (not to be confused with a Hubble bubble), Hubble volume, or Hubble horizon is a conceptual horizon defining the boundary between particles that are moving slower and faster than the speed of light relative to an observer at one given time. Note that this does not mean the particle is unobservable; the light from ...
The Hubble length or Hubble distance is a unit of distance in cosmology, defined as cH −1 — the speed of light multiplied by the Hubble time. It is equivalent to 4,420 million parsecs or 14.4 billion light years. (The numerical value of the Hubble length in light years is, by definition, equal to that of the Hubble time in years.)
Meanwhile, the recession speed is measured through the redshift. Hubble used this approach for his original measurement of the expansion rate, by measuring the brightness of Cepheid variable stars and the redshifts of their host galaxies. More recently, using Type Ia supernovae, the expansion rate was measured to be H 0 = 73.24 ± 1.74 (km/s ...
The light from the smallest, most redshifted galaxies originated nearly 13.8 billion years ago. 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 Earth's orbit is known with an absolute precision of a few meters and a relative precision of a few parts in 100 billion (1 × 10 −11). Historically, observations of Venus transits were crucial in determining the AU; in the first half of the 20th century, observations of asteroids were also important.
seen from Earth +1.86: planet Mars: seen from Earth minimum brightness [42] +1.98: star Polaris: seen from Earth mean brightness [49] +3.03: supernova SN 1987A: seen from Earth in the Large Magellanic Cloud (160,000 light-years away) +3 to +4: Faintest stars visible in an urban neighborhood with naked eye +2 star system T CrB(when nova) seen ...
Volume of the bright inner nebula of the Cat's Eye Nebula [16] 5.5 × 10 46: The volume of a Bok globule like Barnard 68 [19] [20] 4.4 × 10 47: The volume of a Bok globule one light year across [19] [20] 8.47 × 10 47: One cubic light-year ~1.7 × 10 48: Volume of the Oort Cloud, assuming a radius of 50 000 AU ~1.6 × 10 49: Volume of the ...