Galaxies

Galaxies are vast, gravitationally bound systems of stars, gas, dust, and dark matter that drift through the cosmos. Each galaxy can contain billions to trillions of stars orbiting around a common center, often anchored by a supermassive black hole. Our own Milky Way is a spiral galaxy roughly 100,000 light-years across.

Astronomers classify galaxies by shape: spiral (with rotating disks and arms), elliptical (ranging from nearly spherical to flattened), and irregular (disrupted by gravity or collision). Orbital mechanics govern how stars circle galactic centers, while gravitational interactions between galaxies can trigger mergers and reshape them over billions of years.

Galaxies are not uniformly distributed. They cluster together due to gravity, forming cosmic webs of filaments and voids. The most distant galaxies we observe reveal the universe's early history, as their light has traveled for over 13 billion years to reach us. Studying galaxies unlocks secrets about star formation, chemical evolution, and the universe's large-scale structure itself.

Related

Milky Way, Andromeda Galaxy, Redshift, Telescopes, Cosmology, Universe