How many galaxies are there in the universe?

Galaxies are mainly divided into three categories: elliptical galaxies, spiral galaxies and irregular galaxies.

1. Elliptic galaxy: round or oval in shape, with bright center and gradually darkened edges. According to the shape, it can be divided into eight subtypes: E0 to E7. The traditional image of elliptical galaxies is that the star formation process has ended after the initial explosion, leaving only aging stars still shining, but occasionally a small number of stars still form.

Usually, elliptical galaxies look yellow or red, which is very different from light blue spiral galaxies and hot young stars on their spiral arms.

2. Spiral galaxy refers to a flat galaxy with spiral arm structure, which is formed by a lot of gas, dust and hot and bright stars. Spiral galaxy is an extragalactic galaxy with spiral structure, which is denoted by S in Hubble's classification of galaxies.

The spiral shape of the spiral galaxy was first discovered in 1845 when the dog constellation M5 1 was observed.

3. Irregular galaxy refers to a galaxy with irregular shape, no obvious nucleus and spiral arms, no disk-shaped symmetric structure or rotational symmetry, and is represented by the letter Irr. The diameter of irregular galaxies is about 6500 ~ 29000 light years. Among the brightest galaxies in the whole day, irregular galaxies only account for 5%.

Extended data

The formation of galaxies includes two aspects, one is the upper and lower theory, and the other is the upper and lower theory. Upper and lower theory means that galaxies were formed in a big bang, which happened 654.38+03.7 billion years ago.

Another theory holds that galaxies are formed by dust in the universe. Initially, there were many globular clusters in the universe. Later, these stars collided with each other and were destroyed, leaving dust behind. These dust particles combine to form galaxies.

Galaxies vary greatly in size. Elliptical galaxies range in diameter from 3,300 light years to 490,000 light years. The diameters of spiral galaxies range from 654.38+0.6 million light years to 654.38+0.6 million light years. The diameter of irregular galaxies is about 6500 to 29000 light years, and the mass of galaxies is generally between 1 10,000 and 1 trillion times the mass of the sun.

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