Ellipticals - and faint. The dwarf ellipticals may be the...

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Ellipticals Elliptical galaxies are smooth and elliptical in appearance. There are four distinguishing characteristics of the ellipticals: (a) they have much more random star motion than orderly rotational motion (star orbits are aligned in a wide range of angles and have a wide range of eccentricities); (b) they have very little dust and gas left between the stars; (c) this means that they have no new star formation occuring now and no hot, bright, massive stars in them (those stars are too short-lived); and (d) they have no spiral structure. Elliptical galaxies are sub-classified according to how flat they are. The number next to the ``E'' in the tuning fork diagram = 10×(largest diameter - smallest diameter) / (largest diameter), so an E7 galaxy is flatter than an E0 galaxy. The flattened shape is not due to rotational flattening but to how the orbits are oriented and the distribution of the star velocities. Most ellipticals are small
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Unformatted text preview: and faint. The dwarf ellipticals may be the most common type of galaxy in the universe (or maybe the dwarf irregulars are). Examples of elliptical galaxies are M32 (an E2 dwarf elliptical next to the Andromeda Galaxy) and M87 (a huge elliptical in the center of the Virgo cluster). The image sequence below starting from from top left and moving clockwise: Messier 32 (E2 satellite of Andromeda Galaxy), Messier 87 (a huge elliptical at the center of the Virgo cluster), Leo I (=UGC 5470, E3 dwarf elliptical in Local Group), Messier 110 (another satellite of Andromeda Galaxy, E6 type) Messier 32: a dwarf elliptical (E2) satellite galaxy of the Andromeda Galaxy. Courtesy of NOAO/AURA/NSF Messier 87: giant elliptical (E1) at the Virgo Cluster's core. It has grown very large by ``eating'' other galaxies. Leo I: dwarf elliptical (E3) in the Local Group. Messier 110: dwarf elliptical...
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Ellipticals - and faint. The dwarf ellipticals may be the...

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