Cosmic Scale
S301
Star orbiting Sagittarius A* · 26,700 light-years
How big is S301?
S301 is about 2,087,000 km across.
S301 is a star a little bigger than the Sun, discovered in 2026 on the tightest known orbit around Sagittarius A*. Every 8.7 years it plunges to 12 times the Earth–Sun distance from the black hole, fast and close enough that it may reveal how quickly the black hole spins.
At a glance
| Diameter | 2,087,000 km |
|---|---|
| Mass | 2.59 × 10³⁰ kg |
| Diameter compared with Earth | 164 × Earth |
| Distance | 26,700 light-years |
| Orbit | 8.7 years |
| Closest approach | 12 times Earth–Sun |
| Top speed | 25,600 km/s |
Good to know
- At its top speed of 25,600 km/s, over 8% of the speed of light, it would cross from the Earth to the Moon in 15 seconds.
- It was found with the GRAVITY+ instrument on ESO's Very Large Telescope; it next swings past the black hole in 2031.
- It was probably one of a pair: the black hole captured it and flung its partner away.
- Next smaller: Alpha Centauri A · 1,694,000 km
- Next larger: Sirius · 2,381,000 km