Milky Way
The Milky Way is a barred spiral galaxy approximately 100,000 light-years in diameter, containing an estimated 100 to 400 billion stars. Our solar system is located within one of its spiral arms, approximately 26,000 light-years from the galactic center. The galaxy’s structure comprises a central bar, multiple spiral arms, a thick disk, a thin disk, and an extended halo of stars and dark matter surrounding the visible components.
Composition and Dark Matter
The Milky Way is composed of stars, interstellar gas, dust, and a substantial concentration of dark matter. Dark matter comprises roughly 85% of the galaxy’s total mass, though it does not emit or reflect light and remains largely undetectable through direct observation. The nature and distribution of dark matter remain active areas of astronomical research, with observations suggesting a massive dark matter halo extending well beyond the galaxy’s visible disk.
Galactic Dynamics
The galaxy rotates around its center, with different regions exhibiting varying rotation speeds. The central region contains a supermassive black hole known as Sagittarius A*, which influences the motion of nearby stars and gas. The Milky Way is also part of the Local Group of galaxies and continues to interact gravitationally with nearby satellite galaxies, including the Large and Small Magellanic Clouds.
Source Notes
- 2026-04-24: Dark Matter WIMP · ▶ source
- 2026-04-12: JWST Detects Evidence of Universes Primordial Population III Stars in · ▶ source
- 2026-04-13: LHAASOs Confirmation The Universes Most Powerful Cosmic Ray Sources · ▶ source