What is a galaxy? Cosmic spirals of stars

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What is meant by the term galaxy, spirals of stars and interstellar matter scattered throughout the universe, diversity of forms and rotational motion.


Definition of galaxy

A galaxy is a conglomerate made up of millions of stars and interstellar matter.

The Milky Way, a galaxy that affects the earth, has a biconvex lens shape, bulging with spiral arms, with a diameter of about 100,000 light years.


Other galaxies instead have an elliptical shape, spiral or less regular.

In the Universe there are a few billion galaxies which, affected by a motion rotating around an axis that crosses the central nucleus, contribute to the gradual removal of each galaxy from the others due to a global motion of recession.

The galaxies have very large dimensions, varying from those of the dwarf galaxies, containing a few tens of millions of stars, to those of the giant galaxies, which can come to include within their perimeter a number of stars even greater than one thousand billion.

Richard Tuffs: The growth of spiral galaxies over cosmic time (August 2021)


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