Planetary Nebula Minkowski 2-51 + Cluster NGC 7235

Minkowski 2-51
Minkowski 2-51: Planetary nebula in Cepheus; 500 mm Cassegrain 3625 mm f/7.2; SBIG STL11K; 250+50+50+50 min LRGB; Bernese Highlands; © 2015 Radek Chromik


The planetary nebula Minkowski 2-51 (PK 103+0.1) was discovered in 1947 by the German-American astronomer Rudolph Minkowski on photo plates in the Newton focus of the 60 inch or 100 inch telescope on Mount Wilson. Minkowski also contributed to the creation of the National Geographic Society - Palomar Observatory Sky Survey (POSS). [454]

Physical Properties

The distance from M 2-51 is 1941 pc. [145] There is no visual brightness in either SIMBAD or NED. SkySafari 6 says 13.6 mag [149]

«Strasbourg-ESO Catalogue of Galactic Planetary Nebulae» Acker et al., 1992 [141]
DesignationsPN G103.2+00.6: M 2-51, PK 103+00.1, ARO 369, VV 272, VV' 559
Right Ascension (J2000.0)22h 16m 04s
Declination (J2000.0)57° 28' 42"
Dimensions 39." (optical)
Radial Velocity-11.0 km/s ± 25.0 km/s
Expansion Velocity 10.5 km/s (O-III)
C-Star DesignationsAG82 437bis
C-Star Magnitude19.2 mag (B filter), 20.4 mag (V filter)
DiscovererMINKOWSKI 1947

Open Cluster NGC 7234 = NGC 7235

NGC 7234=7235
NGC 7234=7235: Ausschnitt aus dem STScI Digitized Sky Survey [147]

On October 16, 1787, the German-British astronomer William Herschel discovered a star cluster with his self-made 18.7 inch reflecting telescope in Bath, England, which was noted with the designation (WH) VIII 63 and the description «Star clusters, small, poor, little crowded». [464] Unfortunately, Herschel made a mistake when determining his position, because there was nothing at the position given. On September 24, 1829, his son John scoured the same area with his 18.3 inch reflector telescope and recorded a star cluster as h 2154, which he described as «star cluster, pretty much crowded with ruby red star 10th magnitude». [467]

The error in Wilhelm Herschel's position specification was discovered in 1862 by the German astronomer Arthur von Auwers. He recognized that the star clusters WH VIII 63 (GC 4771) and h 2154 (GC 4772) had to be one and the same object and published his findings. But that must have escaped John Herschel when he published his «General Catalogue of Nebulae and Clusters of Stars» in 1864. There the supposedly two star clusters were listed as GC 4771 and GC 4772. Thus, John L. E. Dreyer also adopted this mistake when he published the «New General Catalog of Nebulae and Clusters of Stars» [313] in 1888. There WH VIII 63 was listed as NGC 7234 and JH 2154 as NGC 7235. [196, 277] The error persists to this day. In the SIMBAD Astronomical Database [145] and in the NASA / IPAC Extragalactic Database (NED) [194] only NGC 7235 are listed.

The Swedish astronomer Per Collinder lists the star cluster under the number 477 in his “Catalog of Open Galactic Clusters” published in 1931. He gives an angular size of 5 x 2.5 arc minutes and a number of 12 stars. [455] According to WEBDA [138], the star cluster is 2823 pc away and its age is estimated to be around 12 million years.

«Revised New General Catalogue and Index Catalogue», «Historically Corrected New General Catalogue», Dr. Wolfgang Steinicke, 2021 [277]
NameRADecTypeBmagVmagDimDreyer DescriptionIdentification
NGC 7234 22 12 24.0+57 16 24OCL (II3m), S, P, lCNGC 7235, OCL 229
NGC 7235 22 12 24.0+57 16 24II3m8.67.76.00Cl, pC, has a ruby * 10NGC 7234, OCL 229

Finder Chart

The planetary nebula Minkowski 2-51 is located in the constellation Cepheus. The open star cluster NGC 7235 and the two stars ε Cephei (4.1 mag) and HR 8506 (5.8 mag) help with the search. The best time to observe is May to December, when it is highest at night.

Chart Minkowski 2-51
Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]


138WEBDA, Sternwarte Genf;
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;
194NASA/IPAC Extragalactic Database (NED); (2020-12-27)
196Celestial Atlas by Curtney Seligman; (2020-12-28)
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; (2021-02-17)
313«A New General Catalogue of Nebulae and Clusters of Stars, being the Catalogue of the late Sir John F.W. Herschel, Bart., revised, corrected, and enlarged» Dreyer, J. L. E. (1888); Memoirs of the Royal Astronomical Society. 49: 1–237; Bibcode:1888MmRAS..49....1D
454«NEW EMISSION NEBULAE (II)» R. Minkowski; Publications of the Astronomical Society of the Pacific, Volume 59, Number 350; 1947; DOI:10.1086/125962
455«On Structural Properties of Open Galactic Clusters and their Spatial Distribution. Catalog of Open Galactic Clusters.» Collinder, Per; Annals of the Observatory of Lund, vol. 2, pp.B1-B46, 1931; Bibcode:1931AnLun...2....1C
464«Catalogue of a second thousand of new nebulae and clusters of stars; with a few introductory remarks on the construction of the heavens» William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1789; DOI:10.1098/rstl.1789.0021
467«Catalogue of nebulae and clusters of stars» John Frederick William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1864; DOI:10.1098/rstl.1864.0001