Abell 45
RA/Dec (J2000): 18h 30m 17s, −11° 36′ 54″ (deepskycorner.ch)
Constellation: Scutum (deepskycorner.ch)
Historical / Contextual Notes
- Also catalogued by George O. Abell in 1955; listed in his 1966 follow-up list of old planetary nebulae. (deepskycorner.ch)
- The central star of Abell 45 is very faint — magnitude ~V ~21.1 — making direct detections challenging. (deepskycorner.ch)
- It is a seldom-imaged object; its morphology has been likened in imaging projects to a “wagon wheel” structure due to faint spokes or radial features. (IMAGINGDEEPSPACE.COM)
Physical & Observational Properties
| Property | Value / Description |
| Angular size (optical) | ~ 285″ (~4.75 arcminutes) across the shell. (deepskycorner.ch) |
| Central star magnitude | Very faint: U ~20.5, B ~21.5, V ~21.1 (deepskycorner.ch) |
| Coordinates | RA 18h 30m 17s, Dec −11° 36′ 54″ (deepskycorner.ch) |
| Other designations | PN-G 020.2-00.6, PK 20-00.1, A55 33 (Abell 1955), etc. (deepskycorner.ch) |
| Brightness / visibility | Very low surface brightness; requires dark skies and sensitive equipment. Not bright in blue light; visible often in red/Hα-sensitive imaging. (deepskycorner.ch) |
Key Significance
- Because of its faintness and large shell, Abell 45 is a good example of an evolved planetary nebula, where the nebular gas is diffuse and expanding into the interstellar medium.
- Its faint central star and low contrast make it an astrophotographic challenge and a target suited to narrowband, long exposures.
- The “wagon wheel” morphology hints at internal structure or interaction with local interstellar gas / magnetic fields.
References
“Properties of Some Old Planetary Nebulae” — Abell et al. (1966). (deepskycorner.ch)
DeepskyCorner: Abell 45 (catalog entry). (deepskycorner.ch)
ImagingDeepspace.com: “Abell 45 … unusual morphology likened to wagon wheel.” (IMAGINGDEEPSPACE.COM)
