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.
