Planetary Nebula Merrill 2-1 + Galaxy IC 4538

Merrill 2-1
Merrill 2-1: Image taken with Hubble Space Telescope. Postprocessing by Judy Schmidt [165]


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]
DesignationsPN 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 20s
Declination (J2000.0)-23° 37' 32"
Dimensions 6." (optical), 7." (radio)
Radial Velocity+45.5 km/s ± 5.3 km/s
Expansion Velocity 13.0 km/s (O-III)
C-Star DesignationsAG82 178, CD -23 12238
C-Star Magnitude18.85 mag (B filter)
C-Star Spectral TypeIUE Sp.,P Cyg
DiscovererMERRILL 1942

Galaxy IC 4538

Merrill 2-1 + IC 4538
Merrill 2-1 + IC 4538: Section of PanSTARRS/DR1 color [147]

The spiral galaxy IC 4538 about 15 arcminutes west of Me 2-1 was already discovered on May 26, 1895 by the American astronomer Lewis Swift using the 16 inch Clark Refractor Warner Observatory, Rochester. [277]

«Revised New General Catalogue and Index Catalogue» Dr. Wolfgang Steinicke, 2021 [277]
DesignationIC 4538
TypeGx (SBc)
Right Ascension15h 21m 11.6s
Declination-23° 39' 30"
Diameter2.60 × 2.0 arcmin
Photographic (blue) magnitude12.8 mag
Visual magnitude12.1 mag
Surface brightness13.7 mag·arcmin-2
Position angle32°
Distance derived from z40.3 Mpc
Metric Distance31.65 Mpc
Dreyer DescriptioneeF, vL
IdentificationESO 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 through June.

Chart Merrill 2-1
Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]


141Strasbourg-ESO Catalogue of Galactic Planetary Nebulae; A. Acker, F. Ochsenbein, B. Stenholm, R. Tylenda, J. Marcout, C. Schohn; European Southern Observatory; ISBN 3-923524-41-2 (1992); (2021-02-18)
145SIMBAD astronomical database;
147Aladin Lite; (2020-12-23)
149SkySafari 6 Pro, Simulation Curriculum;
160The STScI Digitized Sky Survey;
165Flickr: Judy Schmidt; (2021-01-02)
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; (2021-02-17)
526«Two Small Planetary Nebulae» Paul W. Merrill; Publications of the Astronomical Society of the Pacific, Volume 54, Number 318, 1942; DOI:10.1086/125472