Cosmic Scale
Stephenson 2-18
Red supergiant · 19,000 light-years
How big is Stephenson 2-18?
Stephenson 2-18 is about 3.0 × 10⁹ km across.
See Stephenson 2-18 in 3D, at true scale
Stephenson 2-18 is a red supergiant near the star cluster Stephenson 2, and one of the largest stars ever proposed. Whether it truly belongs to that cluster is debated — and the answer changes its distance, and so its size.
At a glance
| Diameter | 3.0 × 10⁹ km |
|---|---|
| Diameter compared with Earth | 235,000 × Earth |
| Distance | About 19,000 light-years |
| Surface | 3,200 K |
| Radius | Around 2,150 Suns |
| Type | Red supergiant |
Good to know
- If the size is right, about 10 billion Suns would fit inside it.
- Light would take nearly nine hours to travel around its circumference.
- It lies deep in the galactic plane, so its light reaches us dimmed and reddened by dust.
- Next smaller: WOH G64 · 2.1 × 10⁹ km
- Next larger: Solar System · 9.0 × 10⁹ km