50 Examples of Galaxies - encyclopedia

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Content

Classification
History
Future
Examples of galaxies near Earth
Examples of more distant galaxies

The galaxies they are huge groups of stars that interact gravitationally, and always revolve around a common center. There are hundreds of billions of galaxies in the universe, each containing more than a trillion stars at a time, varying in size, shape and brightness.

The planet Earth, like the entire solar system, belongs to one of all those galaxies called Milky Way (translatable as 'milk road'), which bears that name because seen from Earth, the galaxy looks like a milk stain in the sky.

What are they made of? Stars, gas clouds, planets, cosmic dust, dark matter, and energy are the elements that necessarily appear in a galaxy.At the same time, some substructures such as nebulae, star clusters, and multiple star systems make up galaxies.

Classification

The different forms of the galaxies give rise to a morphological classification, from which each group has in turn some characteristics.

Spiral galaxies: They owe their name to the shape of their disks in which stars, gas and dust are concentrated in spiral arms, extending outward from the central nucleus of galaxies. They have spiral arms looped more or less tightly around a central core, and are rich in gas and dust with a high rate of star formation.
Elliptical galaxies: They contain rather old stars, and therefore do not have gas or dust.
Irregular galaxies: They do not have a particular shape and are among them the smallest galaxies.

History

The Persian astronomer is usually pointed out al-Sufi as the first to intuit the existence of galaxies, and then to the French Charles Messier as the first compiler, at the end of the century XVIII, of non-stellar objects that included around thirty galaxies.

All galaxies have an origin and an evolution, the first having formed about 1000 million years after the big-bang. The training occurred from the atoms hydrogen and helium: with fluctuations of density is that the largest structures began to appear, which then gave rise to galaxies as they are known today.

Future

In the future, it is to be expected that new generations of stars will be produced as long as spiral galaxies have molecular clouds of hydrogen in their arms.

This hydrogen is not unlimited but has a finite supply, so once the formation of new stars is exhausted it will come to an end: in galaxies like the Milky Way, it is expected that the current era of star formation continues for the next hundred billion years, to decline when the smaller stars begin to fade.