We have only known for a short time that there are other galaxies besides our own. During the so-called Great Debate of 1920, astronomers Harlow Shapley and Heber Curtis were still trying to decide whether the diffuse clouds seen through telescopes were mere gas clouds within our own galaxy or other galaxies like ours.
And as it turned out, those objects were indeed other galaxies separated from us by unimaginable distances. This discovery made us realize for the first time just how devilishly large the universe is: today it is estimated that there are between 100,000 and 200,000 million galaxies in the observable universe that, together, total about 70 trillion stars. That is 70 followed by 21 zeros.
There are several types of galaxy. The most stereotypical image is that of the spiral galaxy, such as the Milky Way or Andromeda, because they are usually more striking and, in addition, they are the most abundant, since they represent 72% of the galaxies near us. Irregular galaxies, without any specific shape, account for 10% of nearby galaxies, while lenticular and elliptical galaxies fill the remaining 15% and 3%, respectively.
But there is a variety of galaxy that, due to its scarcity, is much less known: the ring galaxies. The name of these galaxies comes from their shape: an inconspicuous or almost nonexistent core surrounded by a ring of young stars, separated by empty space.
It is not yet known with certainty how these curious structures are formed. Some suggest that it is the result of the gravitational interaction between a large galaxy and a smaller one after the two collide, while others believe that the central nucleus could have stolen the material that forms the disk of some other galaxy that passed too much close.
Be that as it may, if you like astronomy you might be interested in participating in the Galaxy Zoo project in which you can contribute your bit to astronomical knowledge by classifying real images of galaxies according to a series of patterns offered from the page. To date, the initiative has led to the publication of 48 scientific articles on galaxies.
