Theia 558
0.32
UTI
0.5
CN
0.15
Cdens
0.5
CC3
0.23
Clit
1.0
Cdup
Nm (P>50%)
50
Core radius and density
2.3 [pc], 0.7 [pc-2]
- CN 0.5 Moderately populated
- Cdens 0.15 Very loose
- CC3 0.5 Intermediate quality
- Clit 0.23 Rarely studied
- Cdup 1.0 Unique
đĨ Members
đ Colab
đŦ Bayestar19
MOCA
đ CDS
đ Simbad
đ CDS (Îą, δ)
đ Simbad (Îą, δ)
MOCA
đ CDS
đ Simbad
đ CDS (Îą, δ)
đ Simbad (Îą, δ)
Overview
Theia 558 is a moderately 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, but with a large variance across recent sources for the absorption and age parameters (see Parameters). It is rarely studied in the literature.
Data
| Reference | Year | RA [deg] | DEC [deg] | Plx [mas] | pmRA [mas/yr] | pmDE [mas/yr] | Rv [km/s] |
|---|---|---|---|---|---|---|---|
| UCC | 99999â | 95.945 | 3.673 | 1.407 | -0.692 | -1.813 | 0.459 |
| Yan et al. | 2026 | 95.905 | 3.67 | 1.41 | -0.685 | -1.827 | â |
| Yang et al. | 2025 | 95.905 | 3.67 | â | â | â | â |
| Zhang et al. | 2024 | 95.905 | 3.67 | â | â | â | â |
| Hunt & Reffert | 2024 | 95.905 | 3.67 | 1.41 | -0.685 | -1.827 | -1.075 |
| Cavallo et al. | 2024 | 95.977 | 3.72 | 1.409 | â | â | â |
| Hunt & Reffert | 2023 | 95.905 | 3.67 | 1.41 | -0.685 | -1.827 | -1.075 |
| He et al. | 2022 | 95.953 | 3.644 | 1.406 | -0.651 | -1.81 | â |
| Kounkel & Covey | 2019 | 95.893 | 4.31 | 1.435 | â | â | -15.443 |
đĄ 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] | Bfrac | BSS |
|---|---|---|---|---|---|---|---|---|---|
| UCC | 99999â | 0.66 | 0.65 | 2.11 | 209 | -0.100 | 72 | â | â |
| Yan et al. | 2026 | â | â | â | 241 | â | â | â | â |
| Liu et al. | 2025 | 1.61 | 0.41 | â | 31 | â | â | â | â |
| Yang et al. | 2025 | â | â | â | 204 | -0.100(3) | â | â | â |
| Zhang et al. | 2024 | â | â | â | â | -0.019(1) | â | â | â |
| Hunt & Reffert | 2024 | 0.66 | 0.65 | 2.11 | 202 | â | 72(1) | â | â |
| Cavallo et al. | 2024 | 0.66 | 0.99 | â | 316 | -0.250 | â | â | â |
| Hunt & Reffert | 2023 | 0.66 | 0.65 | 2.11 | 202 | â | â | â | â |
| He et al. | 2022 | â | 1.60 | â | 282 | â | â | â | â |
| Kounkel & Covey | 2019 | 0.70 | 0.50 | â | 214 | â | â | â | â |
(N): Indicates that there are N extra values assigned to this parameter in the corresponding reference.
Yan et al. (2026)
Number of WDs: expected from single-star evolution N=5, with probability of formation through binary evolution >=0.5 N=0.
Liu et al. (2025)
Classified as primordial binary cluster 307 along with OC_0343.
Palma et al. (2025)
Classified as optical pair P559, along with OC_0343.
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).