Space Encyclopedia
🌌 Galaxies & Nebulas
Overview
A galaxy is a gravitationally bound system of stars, gas, dust, and dark matter. Our own Milky Way contains 100–400 billion stars. Nebulas are clouds of that gas and dust — some are stellar nurseries, others are the shrouds left behind by dying stars.
Key facts
- •Milky Way diameter: ~100,000 light-years
- •Nearest large galaxy: Andromeda (M31), 2.5 million ly
- •Estimated galaxies in the observable universe: >2 trillion
- •Galaxy types: spiral, elliptical, irregular, lenticular
- •Famous nebulas: Orion (M42), Eagle (M16), Crab (M1)
Why it matters
Galaxies are the largest structures we can see with amateur equipment. Under a dark sky, the Milky Way stretches from horizon to horizon and the Andromeda Galaxy is visible with the naked eye — 2.5 million-year-old photons reaching your retina.
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Frequently asked questions
Can I see another galaxy with the naked eye?
Yes — the Andromeda Galaxy (M31) is visible as a faint smudge from dark-sky locations in the Northern Hemisphere. The Magellanic Clouds are visible from the Southern Hemisphere.
What's the difference between a galaxy and a nebula?
A galaxy is a huge system of stars, gas, and dark matter — often hundreds of billions of stars. A nebula is a cloud of gas and dust inside a galaxy, much smaller and lower-mass.
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