Edwin Hubble (1889-1953) was the responsible one for the classification of the galaxies as we know today.
It was who proved, in years 20, that they are as “islands”, moving itself separately.
The ones are its also that they make possible to identify the relation in the distance enters and speed with that if they put into motion, reason this known as constant Hubble.
The astronomer was formed itself in right for the University of Oxford and appends later left for astronomy, its true passion.
He knows more:
The galaxy is a collection of solar masses that can contain between 100 a thousand and 3,000 billion stars.
They congregate in groups and supergroups and possess some forms.
Nobody knows with precision how many galaxies exist in the Universe, but ours, the Way Láctea, she is only one between thousand or perhaps millions.
The Way Láctea is a galaxy in spiral that if extends for 100 a thousand year-light of diameter.
The galaxies in spiral tend to possess shining younger stars e, while the elliptical galaxies, that are most common, contain older stars.
Andrômeda is many times described as our twin galaxy, because it has more or less the same so great, the same form and age.