What is a large cloud of dust and gas in space known as?

A large cloud of dust and gas in space is known as a nebula. Nebulae are often the birthplaces of stars and can vary in size and density. They can be composed of hydrogen, helium, and other ionized gases. The dust in these clouds can obscure light from stars, leading to the term "dark nebula" when they block light from objects behind them.

In the context of stellar formation, a nebula is critical because the gravitational forces within the cloud can cause it to collapse and condense over time, resulting in the formation of new stars and planetary systems. Some nebulae are also remnants of supernova explosions which scatter elements across the cosmos, contributing to the formation of new celestial bodies.

While asteroids and comets are also significant celestial objects, they do not represent large clouds of dust and gas. An asteroid belt, for example, is a region populated by numerous asteroids primarily made of rock and metal, while comets are icy bodies that can grow tails when nearing the sun. A galaxy, on the other hand, is a vast collection of stars, stellar remnants, interstellar gas and dust, and dark matter held together by gravity, and encompasses thousands or millions of star systems, which is a