The clusters sometimes called open clusters have a

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The _____________ clusters, sometimes called open clusters, have a more formless appearance and possess little or no spherical symmetry or central concentration. Irregular. The irregular clusters sometimes have several small sub-condensations and resemble loose swarms of small clusters. They contain all kinds of galaxies --- spirals, elliptical, and irregulars. Irregular clusters are more numerous than the regular clusters and range from rather rich aggregates of more than a thousand galaxies to small groups of a few dozen members or less.
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Below is the Virgo Cluster, the closest cluster of galaxies to our Milky Way Galaxy: The cluster of galaxies to which our galaxy belongs is called the __________ group. : Local. The Local Group comprises over thirty-five galaxies. The two most massive galaxies of the Local Group are the Milky Way and the Andromeda Galaxy. Beyond the Local Group, at distances of a few times its diameter, we find other similar small groups of ____________. Explanation: Galaxies. The nearest rich cluster of neighboring galaxies is the Virgo cluster, so named because it is in the direction of the constellation Virgo. Comprising approximately 1,300 member galaxies, the cluster forms the heart of the larger local Local Supercluster, of which the Local Group is an outlying member. Considerable matter exists in _______________ space that is not associated with a galaxy or cluster. Explanation: Intergalactic. It is assumed that such matter exists outside any specific area for three reasons: If galaxies have formed from gas and dust, some of this pre-galaxian material could well have been left over; individual, rapidly moving stars occasionally escape from galaxies and from star clusters; and collisions or tidal interactions between galaxies could sweep interstellar matter from them. A theory about the origin and development of the universe is called a _______________. Explanation: Cosmogony. This study refers to theories of the creation of the universe (cosmos). It differs from cosmology in that cosmology is the science of the universe; cosmology includes cosmogony, but it seeks to do much more-- explain the composition of the universe and the laws governing it, while cosmogony seeks to simply explain how the universe came to be.
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The term ______________ embraces not only cosmogony, but also the content and organization of the universe. Explanation: Cosmology. Cosmology is a study of the universe as a whole--what happened in its past and what will happen in the future. The ____________ velocity of galaxies is the component of relative velocity that lies in the line of sight. Explanation: Radial. Remember that velocity consists not only of speed, but also of direction. The radial velocity of a galaxy is its velocity in the line of sight, or in other words its speed straight towards you or away from you. Evidence from the radial velocities of the galaxies acknowledges that the universe is expanding. The first radial velocities of galaxies were measured by V. M. Slipher at the Lowell Observatory.
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