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]}

«Strasbourg-ESO Catalogue of Galactic Planetary Nebulae» Acker et al., 1992 ^[141]
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)	15^h 22^m 19^s
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]

Revised+Historic NGC/IC Version 22/9, © 2022 Dr. Wolfgang Steinicke ^[277]
Designation	IC 4538
Type	Gx (SBc)
Right Ascension (J2000.0)	15^h 21^m 11.6^s
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 March to June.