Collinder 21

0.22 UTI

0.32

C_N

0.03

C_dens

0.62

C_C3

0.06

C_lit

1.0

C_dup

N_m (P>50%) 32

Core radius and density 6.0 [pc], 0.2 [pc^-2]

C3 classification AC

C_N 0.32 Poorly populated
C_dens 0.03 Very loose
C_C3 0.62 Intermediate quality
C_lit 0.06 Rarely studied
C_dup 1.0 Unique

📥 Members 📊 Colab 🔬 Bayestar19

MOCA 🔍 CDS 🔍 Simbad 🔍 CDS (α, δ) 🔍 Simbad (α, δ)

Overview

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Collinder 21 is a poorly populated, very loose object of intermediate C3 quality. Its parallax locates it at a moderate^* distance, well below the mid-plane, affected by low extinction. It is catalogued as an old cluster (see Parameters). It is rarely studied in the literature, with no articles listed in the last 8 years.

(*): The parallax distance estimate (~3.49 kpc) differs significantly from the median photometric distance (~1.40 kpc).

⚠️ Warning: the low UTI value and no obvious signs of duplication (C_dup=1.0) indicate that this is quite probably an asterism, moving group, or artifact, and not a real open cluster.

Relatively close Low extinction Old

Bica et al. (2019)
Web updates in DAML02, some were later removed (2003 to 2010).

Dias et al. (2002)
Asterism (Villanova, S. et al. 2004, A&A 428, 67); cat V3.5 (Jan 2016)

Data

🔍 Search references for Collinder 21 in: SciX Simbad

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Reference	Year	RA [deg]	DEC [deg]	Plx [mas]	pmRA [mas/yr]	pmDE [mas/yr]	Rv [km/s]
UCC	99999–	27.517	27.247	0.286	0.025	-1.145	–
Dib et al.	2018	27.54	27.115	–	–	–	–
Joshi et al.	2016	27.54	27.115	–	–	–	–
Lynga	1987	27.531	27.243	–	–	–	–

💡 Note: The UCC values are estimated from its identified members.

Reference	Year	Dist [kpc]	Av [mag]	DAv [mag]	Age [Myr]	[Fe/H] [dex]	Mass [Msun]	B_frac	BSS
UCC	99999–	1.4	0.63	–	2472	–	–	–	–
Dib et al.	2018	1.40	–	–	2472	–	–	–	–
Joshi et al.	2016	1.40	0.63	–	2472	–	–	–	–

Visualization

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