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The giant elliptical galaxy ESO 325-4. An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. They are one of the three main classes of galaxy described by Edwin Hubble in his Hubble sequence and 1936 work The Realm of the Nebulae, [1] along with spiral and lenticular galaxies.
At the centre of the Hubble tuning fork, where the two spiral-galaxy branches and the elliptical branch join, lies an intermediate class of galaxies known as lenticulars and given the symbol S0. These galaxies consist of a bright central bulge, similar in appearance to an elliptical galaxy, surrounded by an extended, disk-like
De Vaucouleurs argued that Hubble's two-dimensional classification of spiral galaxies—based on the tightness of the spiral arms and the presence or absence of a bar—did not adequately describe the full range of observed galaxy morphologies. In particular, he argued that rings and lenses are important structural components of spiral galaxies ...
Elliptical galaxies are spherical or elliptical in appearance. Spiral galaxies range from S0, the lenticular galaxies, to Sb, which have a bar across the nucleus, to Sc galaxies which have strong spiral arms. In total count, ellipticals amount to 13%, S0 to 22%, Sa, b, c galaxies to 61%, irregulars to 3.5%, and peculiars to 0.9%.
Supergiant elliptical galaxies are some of the largest galaxies known. The Condor Galaxy is a colossal spiral galaxy disturbed by the smaller IC 4970 . It is the largest known spiral galaxy with the isophotal diameter of over 717,000 light-years (220 kiloparsecs ).
Despite the prominence of large elliptical and spiral galaxies, most galaxies are dwarf galaxies. [105] They are relatively small when compared with other galactic formations, being about one hundredth the size of the Milky Way, with only a few billion stars.
This contrasts greatly with elliptical galaxies. Subsequent studies (using the Hubble Space Telescope) show that the bulges of many galaxies are not devoid of dust, but rather show a varied and complex structure. [3] This structure often looks similar to a spiral galaxy, but is much smaller. Giant spiral galaxies are typically 2–100 times the ...
Grand design spiral galaxy – Spiral galaxy with prominent and well-defined spiral arms; Intermediate spiral galaxy – Galaxy type intermediate between a spiral galaxy and barred spiral galaxy; Lenticular galaxy – Class of galaxy between an elliptical galaxy and a spiral galaxy; Ring galaxy – Galaxy with an annular appearance