Theia 2018

0.21 UTI

0.39

C_N

0.04

C_dens

0.5

C_C3

0.06

C_lit

1.0

C_dup

N_m (P>50%) 39

Core radius and density 2.2 [pc], 0.2 [pc^-2]

C3 classification BB

C_N 0.39 Poorly populated
C_dens 0.04 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 2018 is a poorly populated, very loose object of intermediate C3 quality. Its parallax locates it at a moderate distance, below the mid-plane, affected by moderate extinction. It is catalogued as a metal-rich, young cluster (see Parameters). It was recently reported in the literature.

Note: This object shares a significant percentage of members with a later reported entry. 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.

Distant Moderate extinction Metal-rich Young

Liu et al. (2025)
Classified as tidal capture (resonant trapping binary) 360 along with UBC_231.

Palma et al. (2025)
Classified as optical pair P573, along with UBC_231.

Cavallo et al. (2024)
Gold sample.

Hunt & Reffert (2024)
Classified as open cluster. CMD class: 0.99 (50th percentile).

Hunt & Reffert (2023)
Classified as open cluster. CMD class: 0.99 (50th percentile).

Data

🔍 Search references for Theia 2018 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–	116.087	-26.914	0.311	-1.855	2.485	–
Hunt & Reffert	2024	116.087	-26.871	0.319	-1.839	2.476	–
Cavallo et al.	2024	116.074	-26.898	0.319	–	–	–
Hunt & Reffert	2023	116.087	-26.871	0.319	-1.839	2.476	–

💡 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–	3.2	1.09	1.0	68	0.640	273	–	–
Liu et al.	2025	4.15	0.38	–	59	–	–	–	–
Hunt & Reffert	2024	2.80	1.12	1.00	68	–	273⁽¹⁾	–	–
Cavallo et al.	2024	3.60	1.06	–	100	0.640	–	–	–
Hunt & Reffert	2023	2.80	1.12	1.00	68	–	–	–	–

(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 4354	61.5	116.1	-26.87	0.32	-1.85	2.49	–	0.0

💡 Note: The % column shows the percentage of members that Theia 2018 shares with each listed object.

Visualization

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