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  2. Redshift - Wikipedia

    en.wikipedia.org/wiki/Redshift

    The redshift observed in astronomy can be measured because the emission and absorption spectra for atoms are distinctive and well known, calibrated from spectroscopic experiments in laboratories on Earth. When the redshift of various absorption and emission lines from a single astronomical object is measured, z is found

  3. Gravitational redshift - Wikipedia

    en.wikipedia.org/wiki/Gravitational_redshift

    In astronomy, the magnitude of a gravitational redshift is often expressed as the velocity that would create an equivalent shift through the relativistic Doppler effect. In such units, the 2 ppm sunlight redshift corresponds to a 633 m/s receding velocity, roughly of the same magnitude as convective motions in the Sun, thus complicating the ...

  4. Hubble's law - Wikipedia

    en.wikipedia.org/wiki/Hubble's_law

    The redshift z is often described as a redshift velocity, which is the recessional velocity that would produce the same redshift if it were caused by a linear Doppler effect (which, however, is not the case, as the velocities involved are too large to use a non-relativistic formula for Doppler shift).

  5. Angular diameter distance - Wikipedia

    en.wikipedia.org/wiki/Angular_diameter_distance

    The angular size redshift relation for a Lambda cosmology, with on the vertical scale megaparsecs. The angular size redshift relation describes the relation between the angular size observed on the sky of an object of given physical size, and the object's redshift from Earth (which is related to its distance, d {\displaystyle d} , from Earth).

  6. List of common astronomy symbols - Wikipedia

    en.wikipedia.org/wiki/List_of_common_astronomy...

    α - RA, right ascension, if the Greek letter does not appear, á letter will appear. δ - Dec, declination, if the Greek letter does not appear, ä letter will appear. P or P orb or T - orbital period; a - semi-major axis; b - semi-minor axis; q - periapsis, the minimum distance; Q - apoapsis, the maximum distance; e - eccentricity; i ...

  7. Redshift survey - Wikipedia

    en.wikipedia.org/wiki/Redshift_survey

    In astronomy, a redshift survey is a survey of a section of the sky to measure the redshift of astronomical objects: usually galaxies, but sometimes other objects such as galaxy clusters or quasars. Using Hubble's law, the redshift can be used to estimate the distance of an object from Earth. By combining redshift with angular position data, a ...

  8. Recombination (cosmology) - Wikipedia

    en.wikipedia.org/wiki/Recombination_(cosmology)

    Shortly after recombination, the photon mean free path became larger than the Hubble length, and photons traveled freely without interacting with matter. [16] For this reason, recombination is closely associated with the last scattering surface, which is the name for the last time at which the photons in the cosmic microwave background ...

  9. Redshift quantization - Wikipedia

    en.wikipedia.org/wiki/Redshift_quantization

    Redshift quantization, also referred to as redshift periodicity, [1] redshift discretization, [2] preferred redshifts [3] and redshift-magnitude bands, [4] [5] is the hypothesis that the redshifts of cosmologically distant objects (in particular galaxies and quasars) tend to cluster around multiples of some particular value.