Universe

The galaxies

The galaxies

The galaxies They are large structures of the Universe where stars, nebulas, planets, gas clouds, cosmic dust and other materials that are held together by gravitational attraction are grouped together.

For most of our history, humans could only see galaxies as diffuse spots in the night sky.

Our Solar System is part of a galaxy, the only one we have seen from within: The Milky Way. We've always known her, although in ancient times nobody knew what it was. It appears as a whitish strip that crosses the sky, that's why we call it milk road.

Actually the names galaxy and Milky Way They have the same origin. The Greeks considered that the stars were the drops of milk spilled by the goddess Hera while feeding Hercules.

Within the Milky Way we can find various star formations and interstellar dust. The most notable are the nebulae and star clusters. Presumably they also exist in other galaxies.

Galaxies are classified according to their size and shape. There are from dwarfs, with "only" tens of millions of stars, to giants that contain billions of stars. As for the shapes, they can be elliptical, spiral (like the Milky Way), lenticular or irregular.

In the observable Universe there are at least 2 billion (with "b", two million millions) of galaxies, most with sizes ranging from 100 to 100,000 parsecs diameter. Many of them are grouped into clusters of galaxies, and these, in turn, in superclusters.

It is estimated that up to 90% of the mass of each galaxy is somewhat different from ordinary matter; it exists, but it cannot be detected, although its effects are. It is called dark matter Because it doesn't emit light. At the moment it is only a theoretical concept that serves to explain galactic behavior.

Sometimes one galaxy approaches another and they end up crashing, but they are so large and expanded that they can merge with hardly any collisions between the bodies that form them. Or, on the contrary, great cataclysms occur. In any case, as matter tends to condense because of gravity, fusion usually leads to the birth of new stars.

But how is a galaxy? How many types of galaxies are there? That contain? How do they form? On the following pages there are galactic responses.

In this chapter:

The Galaxies of the Universe: The galaxies of the Universe are huge accumulations of stars, gases and dust ... Read pageGlass classes: When using powerful telescopes, in most galaxies only the mixed light of ... Read pageActive galaxies are detected: The Galaxies are not stable, on the contrary: they grow and move, that is, they are active. Some more and others not so much ... Read pageThe nearby galaxies: The closest galaxies to the Milky Way, our neighbors, are those that belong to the so-called Local Group ... Read pageThe Local Group: The nearby galaxies are attracted by the effect of their gravity and grouped in clusters. The smallest clusters are called groups ... Read pageThe Milky Way: The Milky Way galaxy is the one that contains the Solar System and, therefore, the Earth. It is part of the Local Group ... Read page What is the Milky Way ?: If we could observe the Milky Way from outside it, we would see the bulky, yellow and bright center ... Read page Star clusters: The stars do not appear in isolation, but forming groups that we call "clusters ... Read page Nebulas: Nebulas are structures of gas and interstellar dust. Depending on whether they are more or less dense, they are visible, or not, from Earth ... Read page Types of nebulae: One of the most notable aspects of The nebulae is its variety of shapes and structures ... Read pageWhat is an emission nebula ?: The emission nebulae are large clouds of gas and interstellar dust, where stars are born ... Read pageWhat is a dark nebula ?: In the cold areas of the Cosmos, where gas and interstellar dust are very abundant, usually occur ... Read pageThe distant galaxies: The farthest galaxies are more than 13,000 million years old l uz of our Milky Way, almost at the limit… Read page Star clusters: Clusters of galaxies are gigantic structures of the Universe. Galaxies emit a lot of gravity… Read page Astronomical catalogs: Astronomical catalogs are lists of deep space objects that occupy a fixed position in the sky… Read page