While more than two thirds of the most conspicuous

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While more than two-thirds of the most conspicuous galaxies in the sky are spirals, there are many dwarf galaxies which fall into the class of ______________ galaxies. Explanation: Elliptical. Elliptical galaxies are spherical or ellipsoidal systems which consist entirely of stars with no trace of spiral arms. The distribution of ________________ in a typical elliptical galaxy shows that while it has many stars concentrated toward its center, a sparse scattering of stars extends for very great distances and merges imperceptibly into the void of intergalactic space. : Light. This scattering of outlying stars makes determining the total size of an elliptical galaxy difficult. The fact that elliptical galaxies are not disk-shaped shows that they are not rotating as rapidly as the spirals. Elliptical galaxies have a much greater range in size, mass, and _______________ than do the spirals. Explanation: Luminosity. The rare giant ellipticals, such as M87, are more luminous than any known spiral.
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Below is a photo of M87; the light in the upper left is of the stars that make up the galaxy, while what you see extending away from that light towards the lower right is a jet of matter ejected from the galaxy, possibly due to a black hole: Elliptical galaxies range in size from the giants (such as M87 mentioned in the last question) to __________, which are believed to be the most common kind of galaxy. Explanation: Dwarfs. There are so few bright stars in this type of galaxy that even its central regions are transparent. The total number of stars, however, may be as many as several million. Below is a pic of M110, a dwarf elliptical galaxy and the last object to be added to the Messier catalog:
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About three percent of the brightest appearing galaxies in the northern sky are classified as _____________. Explanation: Irregular. They show no trace of circular or rotational symmetry. Their appearance is irregular and chaotic: The continuity of the morphological forms of galaxies along classification sequences suggests that these different forms might represent stages of _______________ for galaxies. Explanation: Evolution. Elliptical galaxies may always have been elliptical, but they may have had supergiant stars when they were young. Spirals may never become elliptical, but eventually their spiral arms may disappear when virtually all of their interstellar matter is converted into stars. However, the evolution of galaxies is still speculative due to the youth of Astronomy. ______________ of galaxies can be roughly classified into two categories: regular clusters and irregular clusters. : Clusters. Almost all galaxies may be members of groups of clusters. Clusters of galaxies are now regarded as fundamental condensations of matter in the universe. The ______________ clusters have spherical symmetry and show marked central concentration. : Regular. They tend to be very rich clusters and most of them probably contain at least a thousand members. The regular clusters have structures resembling those of globular star clusters. Regular clusters consist almost entirely of elliptical galaxies.
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