Nebula
Sh2-172
H II region
A cloud of ionised hydrogen (H II region): a stellar nursery glowing in the ultraviolet light of the young, hot O and B stars inside it. The distance follows from the gas’s radial velocity and the Galaxy’s rotation curve (kinematic method).
| Type | Nebula |
|---|---|
| Constellation | Cassiopeia |
| Distance | 3,510 pc (11.4 thousand ly) · estimated |
| Diameter | 26.2 ly |
| WISE name | G118.621-01.329 |
| Catalogue status | Known H II region |
| Source | WISE H II Catalog v3.0 |
| Right ascension (J2000) | 0h 15m 29.6s |
| Declination (J2000) | +61° 14′ 30″ |
In the sky
Visible from the whole Northern Hemisphere and south to latitude 29° S. North of latitude 29° N it never sets. It stands highest at midnight in September, the best time to observe it.
Through a telescope from Earth
Light's journey
The light you see tonight set out 11 thousand years ago. At that time the first farming villages were being founded; there was no writing yet. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 203 million years.