Supernova
(HC40) (SNR G54.4-0.3)
Supernova remnant
The shock wave of a supernova expanding at thousands of kilometres per second: it sweeps up and heats the interstellar gas and shines in radio waves. The distance is estimated from the radio surface-brightness–diameter (Σ–D) relation and may be off by a factor of two.
| Type | Supernova |
|---|---|
| Constellation | Sagitta |
| Distance | 3,720 pc (12.1 thousand ly) · estimated |
| Diameter | 141.6 ly |
| Type | Shell type |
| Radio flux (1 GHz) | 28 Jy |
| Source | Green's SNR Catalogue |
| Right ascension (J2000) | 19h 33m 20.0s |
| Declination (J2000) | +18° 55′ 59″ |
In the sky
Visible from the whole Northern Hemisphere and south to latitude 71° S. North of latitude 71° N it never sets. It stands highest at midnight in July, the best time to observe it.
Through a telescope from Earth
Light's journey
The light you see tonight set out 12 thousand years ago. At that time Homo sapiens was spreading out of Africa; there was no farming yet. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 215 million years.