What It Is
The Milky Way is our home galaxy: a large barred spiral system of stars, gas, dust, planets, and dark matter bound together by gravity. From Earth, we see its disk from inside, so it appears as a pale band crossing dark skies.
History
The Milky Way got its name from the faint, milky band visible across the sky. Modern telescopes revealed that band as the edge-on view through our own galactic disk rather than a nearby cloud or atmospheric glow.
Science Notes
- The Milky Way spans more than 100,000 light-years and contains roughly 100 to 400 billion stars.
- A supermassive black hole, Sagittarius A*, sits at the center of the galaxy.
- Our solar system takes roughly 240 million years to complete one orbit around the Milky Way.
- age
- ~10-13.6 billion years for most large galaxies; oldest Milky Way populations are ancient
- diameter
- >100,000 light-years across
- stars
- ~100-400 billion stars
- solarOrbit
- The solar system orbits the galactic center about once every 240 million years
- location
- Earth sits in the Milky Way disk, along a spiral arm roughly halfway from the galactic center
