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Most people with even a passing interest in science or science fiction have
heard of the word "galaxy" and probably know that it has to do with a bunch of
stars lumped together in one unit. Understanding galaxies in detail, however,
is one of the most important triumphs in astrophysics, because galaxies are the
unit with which we measure the Universe.
Hubble went on to produce his famous "Hubble Types" which cataloged galaxies into a sequence leading from elliptical galaxies to spiral galaxies, with roughly 20 different categories. In the 1950's the greatest contributions to our understanding of galaxies were observationally spearheaded by Allan Sandage, whose crowning work was the "Hubble Atlas of the Galaxies," which gorgeously illustrated the different Hubble types. In the seventies, astronomers first nailed down the concept of "dark matter" within galaxies, which gravitationally binds the orbits of the stars within them, and increases the masses of galaxies by a factor of ten. The exact character of this extra matter remains an enigma today, but is so compelling observationally that astronomers take its existence as textbook knowledge. Galaxies populate the Universe in a complicated three-dimensional web of
filaments, sheets and clusters, whose dimensions we're just getting a handle
on. As they interact gravitationally, they move at velocities of up to 1,000
kilometers per Go To Page: 1 2 |
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