Alessi 20

(MWSC 23; FoF 2409; OCSN 141)

0.97 UTI

0.83

C_N

1.0

C_dens

1.0

C_C3

1.0

C_lit

1.0

C_dup

C3 classification AA

Number of members (P>50%) 305

Radius (P>50% members) 23.6 [arcmin]

C_N 0.83 Rich
C_dens 1.0 Very dense
C_C3 1.0 Very high quality
C_lit 1.0 Very well-studied
C_dup 1.0 Unique

📥 Members 📊 Colab 🔬 Bayestar19 🔍 CDS 🔍 Simbad 🔍 CDS (α, δ) 🔍 Simbad (α, δ)

Overview

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Alessi 20 is a rich, very dense object of very high C3 quality. Its parallax locates it at a very close distance, near the mid-plane, affected by low extinction. It is catalogued as a near-solar metallicity, very young cluster, but with a large variance across recent sources for the age and mass parameters (see Parameters). It is very well-studied in the literature.

Very close Low extinction Near-solar metallicity Very young

Almeida et al. (2025)
Mass determination: good fit. Isochrone match: good fit.

Cavallo et al. (2024)
Gold sample.

Data

🔍 Search references for Alessi 20 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	–	2.541	58.71	2.329	8.135	-2.429	-10.208
Li et al.	2025	2.593	58.742	2.311	8.195	-2.341	–
Almeida et al.	2025	2.591	58.741	–	–	–	–
Alfonso et al.	2024	2.541	58.706	2.294	8.114	-2.456	–
Zhang et al.	2024	2.643	58.757	–	–	–	–
Hunt & Reffert	2024	2.643	58.757	2.343	8.117	-2.427	-9.305
Celli et al.	2024	2.593	58.742	–	–	–	–
Cavallo et al.	2024	2.261	58.664	2.336	–	–	–
Hunt & Reffert	2023	2.643	58.757	2.343	8.117	-2.427	-9.305
Qin et al.	2023	2.64	58.77	2.33	8.12	-2.42	-10.04
Just et al.	2023	2.658	58.745	–	–	–	–
He et al.	2022	1.905	58.624	2.333	8.019	-2.471	–
Dias et al.	2021	2.591	58.741	2.315	8.168	-2.365	-4.979
Cantat-Gaudin et al.	2020	2.593	58.742	2.311	8.195	-2.341	–
Cantat-Gaudin & Anders	2020	2.593	58.742	2.311	8.195	-2.341	–
Liu & Pang	2019	2.401	58.664	2.308	8.152	-2.404	–
Dias et al.	2019	2.592	58.742	2.311	8.195	-2.341	-4.314
Soubiran et al.	2018	2.593	58.742	–	–	–	-5.04
Cantat-Gaudin et al.	2018	2.593	58.742	2.311	8.195	-2.341	–
Loktin & Popova	2017	2.64	58.76	–	8.73	-3.11	-11.5
Kharchenko et al.	2016	2.658	58.745	–	–	–	–
Dias et al.	2014	2.642	58.76	–	-0.39	-1.34	–
Kharchenko et al.	2013	2.667	58.748	–	6.34	-2.51	-11.5
Gozha et al.	2012	2.642	58.76	–	–	–	–
Kharchenko et al.	2012	2.667	58.748	–	6.18	-2.37	-11.5
Piskunov et al.	2008	2.637	58.761	–	–	–	–
Kharchenko et al.	2007	2.34	58.67	–	0.3	–	-11.5
Piskunov et al.	2007	2.637	58.761	–	–	–	–
Kharchenko et al.	2005	2.64	58.76	–	7.48	-2.61	–
Dias et al.	2002	2.642	58.76	–	8.73	-3.11	-11.5

💡 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]	Bfr	BSS
Li et al.	2025	0.39	0.99	–	11	-0.152	–	–	–
Almeida et al.	2025	0.42	1.00	–	10	–	150	–	–
Alfonso et al.	2024	0.41	0.60	–	16	-0.103	–	–	–
Zhang et al.	2024	–	–	–	–	-0.059*	–	–	–
Hunt & Reffert	2024	–	–	–	–	–	192*	–	–
Celli et al.	2024	–	–	–	9	–	130	–	–
Cavallo et al.	2024	0.43	1.47	–	5	-0.160	–	–	–
Hunt & Reffert	2023	0.41	0.65	1.51	7	–	–	–	–
Qin et al.	2023	0.65	0.99	–	9	–	–	–	–
Just et al.	2023	–	–	–	38	–	17	–	–
He et al.	2022	–	1.05	–	11	–	–	–	–
Dias et al.	2021	0.42	1.00	–	10	-0.104	–	–	–
Cantat-Gaudin et al.	2020	0.41	0.60	–	9	–	–	–	–
Cantat-Gaudin & Anders	2020	0.43	–	–	–	–	–	–	–
Liu & Pang	2019	–	–	–	9	-0.500	–	–	–
Dias et al.	2019	0.44	0.81	–	9	-0.419	–	–	–
Soubiran et al.	2018	0.43	–	–	–	–	–	–	–
Cantat-Gaudin et al.	2018	0.43	–	–	–	–	–	–	–
Loktin & Popova	2017	0.57	0.68	–	3	–	–	–	–
Kharchenko et al.	2016	0.47	1.18	–	38	–	–	–	–
Kharchenko et al.	2013	0.47	1.18	–	38	–	–	–	–
Gozha et al.	2012	0.45	–	–	3	–	23	–	–
Kharchenko et al.	2012	0.47	1.18	–	39	–	–	–	–
Piskunov et al.	2008	0.45	0.68	–	166	–	55*	–	–
Piskunov et al.	2007	0.45	0.68	–	166	–	14	–	–
Kharchenko et al.	2005	0.45	0.68	–	166	–	–	–	–
Dias et al.	2002	0.60	0.68	–	3	–	–	–	–

(*): Indicates that this parameter is assigned more than one value in the corresponding reference.

Visualization

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