User:SkyFlubbler/sandbox/Pending list of largest galaxies

This is a list of the largest known galaxies, sorted according to their maximum estimated physical diameter.

Caveats
Accurate determination of the sizes of galaxies has still been the subject of intense scientific discussion. For one, galaxies are not characterized to be having a definite boundary, but instead having a lowering concentration of stars with increasing distance from the center. Various methodologies have been utilized to account of taking the physical sizes of galaxies. One of which is by using the definition of the half-light radius, the zone where 50% of the emitted light from the galaxy is released, though various papers as well as the NASA/IPAC Extragalactic Database utilizes values as high as 70% or even 90%.

Technical discrepancies in the determination of the half-light radius for galaxies include as follows:

1. Galaxies which emit light at different wavelengths would create different determinations of the half-light radius. The half-light radius for galaxies which strongly emit wavelengths outside the visible spectrum would have a different measurement when taken solely via the visible light measurement. For this reason, this list covers the sizes together with color-codes representing the methodology used.

2. The largest galaxies are supergiant elliptical galaxies (cD), a classification characterized by an extensive, diiffue halo of stars that stretch far beyond the galactic nucleus, and even merge with their cluster's extragalactic stars. Because of this, the boundary at which a galaxy's radius could be defined is highly uncertain at the very least.