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Size (left) and distance (right) of a few well-known galaxies put to scale. The following is a list of notable galaxies.. There are about 51 galaxies in the Local Group (see list of nearest galaxies for a complete list), on the order of 100,000 in the Local Supercluster, and an estimated 100 billion in all of the observable universe.
For instance, Markarian galaxies, named after Benjamin Markarian, are galaxies with excess blue and ultraviolet emission; [5] galaxies in the Atlas of Peculiar Galaxies are assigned an Arp number after Halton Arp who produced the catalog; etc. Objects in these catalogs are excluded below, except in cases where they carry the name of an ...
Galaxies by type. List of spiral galaxies; List of ring galaxies; List of polar-ring galaxies; List of quasars; Galaxies by association. List of largest galaxies; List of nearest galaxies; Satellite galaxies of the Milky Way; Other characteristics. List of galaxies named after people; List of galaxies with richest globular cluster systems
Many dwarf galaxies may orbit a single larger galaxy; the Milky Way has at least a dozen such satellites, with an estimated 300–500 yet to be discovered. [107] Most of the information we have about dwarf galaxies come from observations of the local group, containing two spiral galaxies, the Milky Way and Andromeda, and many dwarf galaxies.
Sagan goes on to extend the comparison in terms of surface area, explaining that if the Cosmic Calendar were scaled to the size of a football field, then "all of human history would occupy an area the size of [his] hand". [3] A similar analogy used to visualize the geologic time scale and the history of life on Earth is the Geologic Calendar.
This is known as the geocentric model of the Universe, or the Ptolemaic system, named after Ptolemy. [ 14 ] A particularly important early development was the beginning of mathematical and scientific astronomy, which began among the Babylonians , who laid the foundations for the later astronomical traditions that developed in many other ...
Astronomy – studies the universe beyond Earth, including its formation and development, and the evolution, physics, chemistry, meteorology, and motion of celestial objects (such as galaxies, planets, etc.) and phenomena that originate outside the atmosphere of Earth (such as the cosmic background radiation).
Composite image of five galaxies clustered together just 600 million years after the Universe's birth [1]. A galaxy cluster, or a cluster of galaxies, is a structure that consists of anywhere from hundreds to thousands of galaxies that are bound together by gravity, [1] with typical masses ranging from 10 14 to 10 15 solar masses.