Planetary Nebula Merrill 2-1 & Galaxy IC 4538
History
This small planetary nebula Me 2-1 was discovered in 1942 by the American astronomer Paul Willard Merrill while looking through objective-prism photographs taken in 1940 by William C. Miller with the 10-inch telescope on Mount Wilson Observatory. The nebula showed a distinct bright Hα line. He also discovered a second planetary nebula (Me 2-2 in Lacerta). The discovery was confirmed by slit spectrograph pictures taken in 1941 with the 100 inch telescope. Both showed the chief nebular lines to be strong. He described the planetary nebula as a disk with 6 arcseconds in diameter and without a conspicuous nucleus. [526]
Physical Properties
According to Simbad the distance is 6665 pc (21'738 lightyears). The apparent brightness in different bands is: B 12.2 mag, V 12.20 mag, G 18.35 mag, J 13.78 mag, H 13.95 mag, K 13.16 mag. [145]
About 45 arcseconds west of Me 2-1, is the binary star CD-23 12237 (SAO 183407) with a visual magnitude of 9.8 mag. It is an orange star of spectral class K2. It's partner is only 0.1 arcseconds separated. The distance is given with 454-533 pc, so it is much closer and is not related to the PN. [145, 149]
| Designations | PN G342.1+27.5: Me 2-1, PK 342+27.1, ARO 88, ESO 514-12, He 2- 126, Sa 2- 120, StWr 4- 2, VV 72, VV' 124, Wray 16- 176, Y-C 2-18 |
| Right Ascension (J2000.0) | 15h 22m 19s |
| Declination (J2000.0) | -23° 37' 31" |
| Dimensions | 6." (optical), 7." (radio) |
| Radial Velocity | +45.5 ± 5.3 km/s |
| Expansion Velocity | 13.0 (O-III) km/s |
| C-Star Designations | AG82 178, CD -23 12238 |
| C-Star Magnitude | B: 18.85 |
| C-Star Spectral Type | IUE Sp.,P Cyg |
| Discoverer | MERRILL 1942 |
Galaxy IC 4538
The spiral galaxy IC 4538 about 15 arcminutes west of Me 2-1 was already discovered on 26 May 1895 by the American astronomer Lewis Swift using the 16 inch Clark Refractor Warner Observatory, Rochester. [277]
| Designation | IC 4538 |
| Type | Gx (SBc) |
| Right Ascension (J2000.0) | 15h 21m 11.6s |
| Declination (J2000.0) | -23° 39' 30" |
| Diameter | 2.6 × 2 arcmin |
| Photographic (blue) magnitude | 12.8 mag |
| Visual magnitude | 12.1 mag |
| Surface brightness | 13.7 mag·arcmin-2 |
| Position Angle | 32° |
| Redshift (z) | 0.009530 |
| Distance derived from z | 40.25 Mpc |
| Metric Distance | 31.650 Mpc |
| Dreyer Description | eeF, vL |
| Identification, Remarks | ESO 514-10; MCG -4-36-13; UGCA 406; IRAS 15182-2328 |
Finder Chart
The planetary nebula Merrill 2-1 is located in the constellation Libra. The best observation time is in the months December to August.
