What are galaxies? How are they classified?

Question

What are galaxies?  How are they classified?

Leah Abbate · Accepted Answer

Galaxies are huge number of stars bound by gravity.It also contains dust, Gas,dark matter and may be even a black hole.

Edwin Hubble categorized galaxies according to the diagram. Image courtesy of pictures.space.com

Ivy Allen · Answer

undefined Galaxies are massive systems of stars, stellar remnants, interstellar gas, dust, dark matter, and other astronomical objects bound together by gravity. They come in various shapes and sizes, ranging from dwarf galaxies with just a few billion stars to giant galaxies containing trillions of stars.

Galaxies are classified based on their shape, which can be categorized into three main types: spiral galaxies, elliptical galaxies, and irregular galaxies. Spiral galaxies have a distinct spiral structure with a central bulge and spiral arms extending outward. Elliptical galaxies are smooth and ellipsoidal in shape, lacking any prominent features like spiral arms. Irregular galaxies do not have a regular shape and often exhibit chaotic structures. Additionally, galaxies can be further classified based on various properties such as their size, luminosity, and the presence of specific features like bars or rings.