Cassiopeia A
Cassiopeia A is a supernova remnant in the constellation Cassiopeia, about 11,090 light-years from Earth.
Young supernova remnant, a bright radio source
Facts
| Type | Supernova remnant |
|---|---|
| Constellation | Cassiopeia |
| Position (J2000) | 23h 23m 26s, +58° 48′ |
| Distance | 11,090 light-years (its light set off about 11,090 years ago) |
| Brightness | magnitude 14.3 (smaller is brighter; the faintest stars the eye sees are about 6) |
| Size on the sky | 5′ × 5′ (the full Moon is about 31′) |
| Filter | OIII filter (Planetary nebulae and supernova remnants shine mostly in the green light of doubly ionised oxygen: an OIII filter passes it and darkens the sky around it.) |
| Studied in | 3,094 scientific papers (SIMBAD) |
When and how to see it
Cassiopeia A is highest in the sky at midnight in September. From India (about 20° N) it climbs to about 51° above the horizon; from 50° N, to about 81°. To see it you need a large telescope or long-exposure photos.
Heights are worked out for India and for 50° N. Set your location in Settings to see them for where you are.
For tonight's best time from your own town, the darkness and the Moon, open it on the map and see its "Tonight from your location" card.
More in Cassiopeia
- Bubble Nebula
- Fish Head Nebula
- Heart Nebula
- M52 (NGC 7654)
- M103 (NGC 581)
- Pacman Nebula
- Soul Nebula
- Tycho's Supernova
Everything in Cassiopeia · All 88 constellations · All sky objects
Data: SIMBAD (CDS, Strasbourg; the site's weekly copy) · Data sources & credits