The biggest known galaxy is wider than 60 Milky Ways stacked end-to-end. Most galaxies are far smaller.
How to Play: Guess if the galaxy on the right is LARGER or SMALLER than the one on the left.
Name A
Name B
Top 10 Largest Known Galaxies
Galaxy diameters are measured in light-years. Most galaxies are 1,000-200,000 ly across; supergiants can reach 5+ million ly.
| # | Name | Diameter (light-years) | Unit |
|---|---|---|---|
| 1 | IC 1101 (giant elliptical) | 6,000,000 | ly |
| 2 | ESO 444-46 | 2,400,000 | ly |
| 3 | Phoenix Cluster (CGalaxy) | 2,000,000 | ly |
| 4 | Hercules A | 1,500,000 | ly |
| 5 | 3C 348 | 1,500,000 | ly |
| 6 | UGC 2885 (Rubin's Galaxy) | 832,000 | ly |
| 7 | NGC 6872 | 522,000 | ly |
| 8 | Antennae Galaxies | 500,000 | ly |
| 9 | Tadpole Galaxy | 280,000 | ly |
| 10 | M87 (Virgo) | 240,000 | ly |
Galaxy Scale
IC 1101 at 6 million light-years is the largest known galaxy — a supergiant elliptical at the center of a galaxy cluster ~1 billion ly from Earth.
The Milky Way at 100,000 ly is average for spiral galaxies. Andromeda is similar. Both are part of the ‘Local Group’ of about 50 galaxies.
Dwarf galaxies (1,000-10,000 ly) are by far the most numerous. Most galaxies in the universe are dwarfs, even though we see only the largest from far away.
Frequently Asked Questions
Largest known galaxy?
IC 1101 at 6 million light-years across — 60x wider than the Milky Way.
How big is our galaxy?
Milky Way ~100,000 ly diameter, with up to 400 billion stars.
How many galaxies in the universe?
Roughly 100-200 billion observable galaxies, possibly trillions in the unobservable universe.
Are galaxies expanding?
No — galaxies themselves are stable. The space between galaxies is expanding (Hubble expansion).
Note: Galaxy diameters in light-years per published astronomy research.
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