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CAS Parameters
The CAS (concentration, asymmetry, smoothness) parameters are a tool originally developed in astronomy to characterize the shapes and images of objects with some central concentration. Each parameter is a single number which represents some aspect of the structure of the object under study. These parameters were originally developed by astronomers to quantify the light distribution of galaxies, as a way to avoid having to use visual estimates of galaxy morphological classification. They have also been used in biological imaging, and other areas of imaging analysis. Each parameter is measured in a well defined way and within a well defined radius. Asymmetry (A) The asymmetry index is a measure of how symmetric an object is. It is defined by rotating and subtracting an image by 180 deg from its center. This parameter has been used in astronomy to determine galaxy mergers and its history.{{Cite web, url=https://www.scientificamerican.com/article/the-universes-invisible-hand/, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galaxy Morphological Classification
Galaxy morphological classification is a system used by astronomers to divide galaxies into groups based on their visual appearance. There are several schemes in use by which galaxies can be classified according to their morphologies, the most famous being the Hubble sequence, devised by Edwin Hubble and later expanded by Gérard de Vaucouleurs and Allan Sandage. However, galaxy classification and morphology are now largely done using computational methods and physical morphology. Hubble sequence The Hubble sequence is a morphological classification scheme for galaxies invented by Edwin Hubble in 1926. It is often known colloquially as the “Hubble tuning-fork” because of the shape in which it is traditionally represented. Hubble's scheme divides galaxies into three broad classes based on their visual appearance (originally on photographic plates): * Elliptical galaxies have smooth, featureless light distributions and appear as ellipses in images. They are denoted by the l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
