At a distance of approximately 2.73 million light years and containing roughly 40 billion stars, M33 is a spiral galaxy located behind the Triangulum constellation. It is possible this galaxy was discovered 100 years prior to Charles Messier’s independent discovery by the Italian astronomer Giovanni Battista Hodierna.

This particular image of M33 contains exaggerated HII regions, visible as pinkish-red cloudy structures within the galaxy. These regions are emission nebulae, specifically ionized hydrogen. Boosting these regions yields a great visual representation of how these nebulae are arranged throughout other galaxies, as well as a breathtaking photograph.

Wait, what exactly is a galaxy in the first place? Well, they are essentially the largest “building blocks” of the universe. They contain everything that is smaller than them, from nebulae to stars, planets, moons, comets—you name it, it likely resides within a galaxy.