galaxiën

Galaxies are vast, gravitationally bound systems of stars, stellar remnants, interstellar gas, dust, and dark matter. They range in size from dwarf galaxies, containing only a few hundred million stars, to giant galaxies, with up to 100 trillion stars. Our own Milky Way galaxy is a spiral galaxy, estimated to contain between 100 and 400 billion stars.

Galaxies are not uniformly distributed throughout the universe. They are often found in clusters, and these clusters can be part of even larger superclusters. The shape of a galaxy is determined by its formation history and interactions with other galaxies. The three main morphological types are spiral, elliptical, and irregular. Spiral galaxies, like the Milky Way, have a central bulge and a disk with spiral arms. Elliptical galaxies are typically smooth, oval-shaped, and contain older stars. Irregular galaxies lack a distinct shape and often result from gravitational interactions.

The study of galaxies is a fundamental part of astronomy. Scientists use telescopes to observe galaxies, analyze their light to determine their composition, age, and motion, and map their distribution across the cosmos. Understanding galaxies helps us comprehend the structure and evolution of the universe, from its earliest stages to its present state. Dark matter, an invisible substance that interacts only through gravity, is believed to make up a significant portion of a galaxy's mass, influencing its rotation and structure.