In 1936, because of Hubble, galaxies were grouped into four main types: spiral galaxies, lenticular galaxies, elliptical galaxies and irregular galaxies.
Interestingly enough, more than two-thirds of all observed galaxies are spiral galaxies that have a flat, spinning disk with a central bulge surrounded by spiral arms.
Elliptical galaxies contain many older stars, but little dust and other interstellar matter. Their stars orbit the galactic center but they do so in more random directions. The universe’s largest known one may contain up to a trillion stars and span two million light-years across.
Lenticular galaxies, such as the funny Sombrero Galaxy, are between elliptical and spiral galaxies. They have a thin, rotating disk of stars and a central bulge, but they don’t have spiral arms. Like elliptical galaxies, they have little dust and interstellar matter, and they seem to form more often in densely populated regions of space.
The rest of the galaxies are called Irregular – such as the Large and Small Magellanic Clouds. They appear misshapen and lack a distinct form, very often because they are within the gravitational influence of other galaxies close by. They are full of gas and dust, which makes them great nurseries for forming new stars.
Dr. Thomas Hughes is a UK-based scientist and science communicator who makes complex topics accessible to readers. His articles explore breakthroughs in various scientific disciplines, from space exploration to cutting-edge research.
