Galaxies NGC 672, IC 1727 + Open Cluster Collinder 21

NGC 672 + IC 1727
NGC 672 + IC 1727: Galaxy group in Triangulum ; 500 mm Cassegrain 5800mm f11.4; SBIG STL11K; 75-15-15-15 min LRGB; Bernese Highlands; © 2005 Radek Chromik

History

The galaxy NGC 672 was discovered on 26 October 1786 by Wilhelm Herschel with his 18.7 "reflector telescope. Herschel seemed to have overlooked the neighboring galaxy IC 1727 due to its lower luminosity. It was only discovered on 29 November 1896 by Isaac Roberts with a 20" reflector telescope discovered photographically. [277]

Physical Properties

The two galaxies NGC 672 and IC 1727 are physically very close and show gravitational interaction with one another. IC 1727 shows a strong asymmetry in the apparent distribution of young stars, while that of older stars is more even. The galaxy NGC 672 shows no asymmetry in the distribution of stars of different ages. The distance from NGC 672 is estimated at 7.22 ± 0.10 Mpc and that from IC 1727 at 7.14 ± 0.10 Mpc. It is estimated that star formation in the two galaxies occurred in two intervals 20-30 and 450-700 million years ago. [426]

The galaxy NGC 684 was discovered by Wilhelm Herschel on the same night as NGC 672. [277]

Revised+Historic NGC/IC, Version 22/9, © Dr. Wolfgang Steinicke [277]
NameRADecTypebMagvMagDimDreyer DescriptionIdentification, Remarks
NGC 67201 47 54.0+27 25 58Gx (SBc)11.510.96 × 2.4F, pL, mE 80°UGC 1256, MCG 4-5-11, CGCG 482-16, IRAS 01450+2710, VV 338, KCPG 40B
NGC 68401 50 14.1+27 38 46Gx (Sb)13.312.43.2 × 0.6F, vlE, * 13 f 100"IC 165, UGC 1292, MCG 4-5-17, CGCG 482-22, IRAS 01474+2724
IC 172701 47 30.0+27 19 57Gx (SBm)12.111.55.7 × 2.4F, L, st inv, I 157 nfUGC 1249, MCG 4-5-9, CGCG 482-14, VV 338, KCPG 40A
IC 173101 50 12.5+27 11 46Gx (SBc)14.013.31.5 × 1F, E npsf, bM, prob spirUGC 1291, MCG 4-5-18, CGCG 482-21
Collinder 21
Collinder 21: Bottom left: Open cluster with "D" shaped asterism. Top right: pair of galaxies NGC 672 and IC 1727. Section of the DSS2 [147]

Open Cluster Collinder 21

This open cluster with the conspicious "D" shape was discovered in 1931 by the Swedish Astronomer Per Collinder. He counted 12-15 stars and noted: «A small cluster cluster of bright stars, irregular. Cluster probability calculated according to Michell's (255) method = 27:1 This expresses the probability that the grouping is not accidental.» [455]

The distance is estimated to 1400 pc. [145]

Data from Simbad. [145]
Designations Collinder 21, C 0147+270, OCl 371
RA 01 50 9.600
Dec +27 06 54.00
vMag 8.2

Finder Chart

The galaxy pair NGC 672 + IC 1727 is located in the constellation Triangulum, about 40 arc minutes northwest of the small open star cluster Collinder 21. The best observation time is July to February.

Chart Galaxies NGC 672, IC 1727 + Open Cluster Collinder 21
Galaxies NGC 672, IC 1727 + Open Cluster Collinder 21 in constellation Triangulum. Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

More Objects Nearby (±15°)

References

145SIMBAD astronomical database; simbad.u-strasbg.fr/simbad
147Aladin Lite; aladin.u-strasbg.fr/AladinLite (2020-12-23)
149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)
426«Stellar content of the interacting galaxies IC 1727 and NGC 672» Tikhonov, N. A.; Galazutdinova, O. A.; Lebedev, V. S.; Astronomy Letters, Volume 40, Issue 1, pp.11-21, January 2014; DOI:10.1134/S106377371401006X
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