Crab Nebula vs Ring Nebula
A supernova remnant and a planetary nebula, close in catalogue magnitude and far apart in practice. The Crab (M1, NGC 1952) is listed at 8.40 and the Ring (M57, NGC 6720) at 8.80, a margin of 0.4 magnitudes that would suggest the Crab is the easier find. It is not. M1 spreads its light across 8.00 arcminutes and settles near 12.7 magnitudes per square arcminute; M57 compresses the same order of flux into 1.27 arcminutes and reaches about 9.1. The Ring therefore stands out crisply where the Crab appears as a faint grey smudge that many observers struggle to distinguish from the sky.
Property comparison
| Property | Crab Nebula | Ring Nebula |
|---|---|---|
| Object type | Supernova Remnant | Planetary Nebula |
| Catalogue designation | NGC 1952 | NGC 6720 |
| Integrated magnitude | 8.40 | 8.80 |
| Apparent size | 8.0′ (8′) | 1.3′ (1.27′) |
| Mean surface brightness | 12.7 mag/arcmin² | 9.1 mag/arcmin² |
| Position (J2000) | RA 5h, Dec +22° | RA 18h, Dec +33° |
| Sky region | Northern sky | Northern sky |
Mean surface brightness is derived from the integrated magnitude and the apparent diameter; higher values mean a fainter, more diffuse surface.
Full data for each object: Crab Nebula · Ring Nebula
Key differences
Key Differences
- ◆ M1 is nominally brighter at magnitude 8.40 against 8.80 for M57.
- ◆ M57 is compact at 1.27 arcminutes; M1 spans 8.00, over six times wider.
- ◆ Surface brightness diverges sharply — about 9.1 magnitudes per square arcminute for M57 against 12.7 for M1.
- ◆ M1 is a supernova remnant; M57 is a planetary nebula formed by a dying low-mass star.
- ◆ M1 lies at declination +22° in the winter sky; M57 at +33° in the summer sky.