Theia 200

0.18 UTI

0.25

C_N

0.02

C_dens

0.5

C_C3

0.06

C_lit

1.0

C_dup

N_m (P>50%) 25

Core radius and density 3.3 [pc], 0.1 [pc^-2]

C3 classification BB

C_N 0.25 Poorly populated
C_dens 0.02 Very loose
C_C3 0.5 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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Theia 200 is a poorly populated, very loose object of intermediate C3 quality. Its parallax locates it at a close distance, near the mid-plane, affected by low extinction. It is catalogued as a near-solar metallicity, intermediate-age cluster (see Parameters). It is rarely studied in the literature.

Note: This object shares a large percentage of members with 2 later reported entries. See table with shared members information.

⚠️ 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.

Close Low extinction Near-solar metallicity Intermediate age

Palma et al. (2025)
Classified as optical pair P404, along with HSC_1022.

Cavallo et al. (2024)
Gold sample.

Hunt & Reffert (2024)
Classified as open cluster. CMD class: 1.00 (50th percentile).

Hunt & Reffert (2023)
Classified as open cluster. CMD class: 1.00 (50th percentile).

Data

🔍 Search references for Theia 200 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–	18.877	60.756	1.155	2.947	-1.691	-15.76
Hunt & Reffert	2024	18.701	60.75	1.148	2.959	-1.672	-14.795
Cavallo et al.	2024	19.113	60.914	1.148	–	–	–
Hunt & Reffert	2023	18.701	60.75	1.148	2.959	-1.672	-14.795
Kounkel & Covey	2019	24.386	58.529	1.192	–	–	–

💡 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–	0.835	0.89	0.27	155	0.270	75	–	–
Hunt & Reffert	2024	0.83	0.89	0.27	155	–	75⁽¹⁾	–	–
Cavallo et al.	2024	0.89	1.07	–	214	0.270	–	–	–
Hunt & Reffert	2023	0.83	0.89	0.27	155	–	–	–	–
Kounkel & Covey	2019	0.84	0.78	–	70	–	–	–	–

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

Cluster	%	RA	DEC	Plx	pmRA	pmDE	Rv	UTI
CWNU 378	88.0	19.01	60.83	1.15	2.94	-1.68	-14.02	0.02
CWNU 389	40.0	20.2	60.93	1.12	3.0	-1.7	-18.9	0.05

💡 Note: The % column shows the percentage of members that Theia 200 shares with each listed object.

Visualization

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