Platais 9

(MWSC 1639; OCSN 252)

0.78 UTI

0.78

C_N

0.31

C_dens

1.0

C_C3

0.9

C_lit

1.0

C_dup

N_m (P>50%) 172

Core radius and density 3.6 [pc], 1.6 [pc^-2]

C3 classification AA

C_N 0.78 Rich
C_dens 0.31 Loose
C_C3 1.0 Very high quality
C_lit 0.9 Very well-studied
C_dup 1.0 Unique

📥 Members 📊 Colab 🔬 Bayestar19

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

Overview

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Platais 9 is a rich, loose 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, young cluster, but with a large variance across recent sources for the absorption parameter (see Parameters). It is very well-studied in the literature.

Note: This object shares a moderate percentage of members with a later reported entry. See table with shared members information.

Very close Low extinction Near-solar metallicity Young

Yan et al. (2026)
Number of WDs: expected from single-star evolution N=1, with probability of formation through binary evolution >=0.5 N=13.

Palma et al. (2025)
Part of multiple system G138, along with HSC_2068, HSC_2156 and HSC_2139.

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

Cavallo et al. (2024)
Gold sample.

Hunt & Reffert (2024)
Classified as open cluster. CMD class: 0.95 (50th percentile).

Hunt & Reffert (2023)
Classified as open cluster. CMD class: 0.95 (50th percentile).

Hu et al. (2021)
Ellipticities (core, all): e_core=0.1462, e_all=0.1222.

Data

🔍 Search references for Platais 9 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–	138.821	-43.85	5.391	-24.274	13.269	16.115
Yan et al.	2026	138.321	-43.558	5.448	-24.559	13.301	–
Li et al.	2025	139.241	-43.862	5.463	-24.705	13.333	–
Almeida et al.	2025	139.421	-44.161	–	–	–	–
Alfonso et al.	2024	139.383	-43.61	5.423	-24.585	13.34	–
Swiggum et al.	2024	138.321	-43.558	5.448	-24.559	13.301	16.185
Hunt & Reffert	2024	138.321	-43.558	5.448	-24.559	13.301	15.01
Cavallo et al.	2024	139.139	-43.888	5.461	–	–	–
Hunt & Reffert	2023	138.321	-43.558	5.448	-24.559	13.301	15.01
Almeida et al.	2023	139.401	-43.896	–	–	–	–
Qin et al.	2023	139.35	-43.5	5.71	-26.0	13.4	16.44
He et al.	2022	138.689	-44.006	5.369	-24.156	13.126	–
Tarricq et al.	2022	138.374	-43.542	5.38	-24.208	13.242	–
Dias et al.	2021	139.421	-44.161	5.458	-24.699	13.272	16.849
Cantat-Gaudin et al.	2020	139.241	-43.862	5.463	-24.705	13.333	–
Cantat-Gaudin & Anders	2020	139.241	-43.862	5.463	-24.705	13.333	–
Bossini et al.	2019	139.241	-43.862	–	–	–	–
Soubiran et al.	2018	139.241	-43.862	–	–	–	17.02
Cantat-Gaudin et al.	2018	139.241	-43.862	5.463	-24.705	13.333	–
Yen et al.	2018	137.641	-43.885	5.89	-24.62	12.91	–
Dib et al.	2018	137.955	-43.53	–	–	–	–
Joshi et al.	2016	137.955	-43.53	–	–	–	–
Gozha et al.	2012	138.446	-43.74	–	–	–	–
Piskunov et al.	2008	138.536	-44.139	–	–	–	–
Kharchenko et al.	2007	138.45	-43.74	–	3.3	–	17.83
Piskunov et al.	2007	138.536	-44.139	–	–	–	–
van den Bergh	2006	138.446	-43.74	–	–	–	–
Kharchenko et al.	2005	138.54	-44.14	–	-24.53	12.01	17.83
Dias et al.	2002	138.446	-43.74	–	-24.13	13.32	17.83

💡 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–	0.19	0.075	0.62	69	-0.003	702	0.24	–
Yan et al.	2026	–	–	–	50	–	–	–	–
Li et al.	2025	0.20	0.06	–	76	0.048	–	–	–
Almeida et al.	2025	0.18	0.14	–	55	–	80	–	–
Alfonso et al.	2024	0.17	0.00	–	47	-0.025	–	–	–
Swiggum et al.	2024	0.19	–	–	37	–	225	–	–
Hunt & Reffert	2024	0.19	0.09	0.62	37	–	62⁽¹⁾	–	–
Cavallo et al.	2024	0.19	0.61	–	65	0.190	–	–	–
Hunt & Reffert	2023	0.19	0.09	0.62	37	–	–	–	–
Almeida et al.	2023	0.19	0.25	–	69	-0.005	136⁽¹⁾	0.24	–
Qin et al.	2023	0.20	0.22	–	50	–	–	–	–
He et al.	2022	–	0.35	–	63	–	–	–	–
Tarricq et al.	2022	0.17	–	–	50	–	–	–	–
Dias et al.	2021	0.18	0.14	–	55	-0.025	–	–	–
Cantat-Gaudin et al.	2020	0.17	0.00	–	50	–	–	–	–
Kounkel et al.	2020	0.20	0.25	–	81	–	–	–	–
Cantat-Gaudin & Anders	2020	0.18	–	–	–	–	–	–	–
Bossini et al.	2019	0.16	0.00	–	78	0.000	–	–	–
Soubiran et al.	2018	0.18	–	–	–	–	–	–	–
Cantat-Gaudin et al.	2018	0.18	–	–	–	–	–	–	–
Yen et al.	2018	0.19	0.02	–	123	–	–	–	–
Dib et al.	2018	0.20	–	–	123	–	–	–	–
Joshi et al.	2016	0.20	0.00	–	123	–	2754	–	–
Gozha et al.	2012	0.17	–	–	100	–	2754	–	–
Piskunov et al.	2008	0.20	0.00	–	123	–	1644⁽¹⁾	–	–
Piskunov et al.	2007	0.20	0.00	–	123	–	1180	–	–
van den Bergh	2006	0.17	–	–	100	–	–	–	–
Kharchenko et al.	2005	0.20	0.00	–	123	–	–	–	–
Dias et al.	2002	0.17	–	–	100	–	–	–	–

(N): Indicates that there are N extra values assigned to this parameter in the corresponding reference.

Cluster	%	RA	DEC	Plx	pmRA	pmDE	Rv	UTI
CWWDL 14691	41.3	139.07	-43.74	5.41	-24.28	13.23	16.11	0.0

💡 Note: The % column shows the percentage of members that Platais 9 shares with each listed object.

Visualization

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