Theia 1645

0.03 UTI

0.44

C_N

0.22

C_dens

0.75

C_C3

0.06

C_lit

0.09

C_dup

N_m (P>50%) 44

Core radius and density 2.3 [pc], 1.1 [pc^-2]

C3 classification AB

C_N 0.44 Poorly populated
C_dens 0.22 Very loose
C_C3 0.75 High quality
C_lit 0.06 Rarely studied
C_dup 0.09 Very likely duplicate

📥 Members 📊 Colab 🔬 Bayestar19

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

Overview

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Theia 1645 is a poorly populated, very loose object of high C3 quality. Its parallax locates it at a relatively close distance, near the mid-plane, affected by moderate extinction. It is catalogued as a near-solar metallicity, very young cluster, but with a large variance across recent sources for the absorption parameter (see Parameters). It was recently reported in the literature.

⚠️ Warning: This is very likely a duplicate object, which shares a large percentage of members with at least one previously reported entry. See table with shared members information.

Relatively close Moderate extinction Near-solar metallicity Very young

Liu et al. (2025)
Classified as primordial binary cluster 357 along with NGC_6383, and of multiple system 13 along with NGC_6383 and Antalova_2.

Palma et al. (2025)
Part of multiple system G5, along with Antalova_2 and NGC_6383.

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 1645 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–	262.752	-33.48	0.883	2.507	-1.917	-4.183
Liu et al.	2025	262.76	-33.47	0.89	2.44	-1.94	-4.2
Hunt & Reffert	2024	262.758	-33.468	0.89	2.436	-1.936	-4.202
Cavallo et al.	2024	262.653	-33.534	0.891	–	–	–
Hunt & Reffert	2023	262.758	-33.468	0.89	2.436	-1.936	-4.202

💡 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–	1.06	1.57	1.87	16	-0.200	325	–	–
Liu et al.	2025	1.79	0.49	–	15	–	–	–	–
Hunt & Reffert	2024	1.06	1.57	1.87	16	–	325⁽¹⁾	–	–
Cavallo et al.	2024	0.99	1.66	–	9	-0.200	–	–	–
Hunt & Reffert	2023	1.06	1.57	1.87	16	–	–	–	–

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

Cluster	%	RA	DEC	Plx	pmRA	pmDE	Rv	UTI
UFMG 77	90.9	262.79	-33.47	0.88	2.51	-1.9	0.07	0.34
CWWDL 14393	81.8	262.72	-33.48	0.89	2.47	-1.91	0.07	0.06

💡 Note: The % column shows the percentage of members that Theia 1645 shares with each listed object.

Visualization

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