Which characteristics describe a spiral galaxy?

Spiral galaxies are named after their morphology because they have a clear spiral structure around their nucleus when viewed perpendicular to their plane. In censuses they appear as the most common typology.

The spiral galaxies have young and old stars, suggesting that they did not form from another older galaxy or from an ancient clash between two galaxies. In the nucleus there is a predominance of older stars and in the arms there is a greater activity of star formation. In this way, the nuclei of the spiral galaxies have a more orange hue and the arms a more blue hue.

Spiral galaxies have diameters ranging from 20,000 light years to over 100,000 light years. Its masses are estimated to range from 10 billion to 10 trillion times the mass of the Sun. The Milky Way, where the solar system is located, is a large and massive spiral galaxy.