ASCC 20

(MWSC 556)

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0.71 UTI
0.8
CN
0.48
Cdens
1.0
CC3
0.65
Clit
1.0
Cdup
Nm (P>50%) 244
Core radius and density 3.2 [pc], 2.4 [pc-2]
C3 classification AA
  • CN 0.8 Rich
  • Cdens 0.48 Loose
  • CC3 1.0 Very high quality
  • Clit 0.65 Moderately studied
  • Cdup 1.0 Unique
đŸ“Ĩ Members 📊 Colab đŸ”Ŧ Bayestar19 MOCAMOCA 🔍 CDS 🔍 Simbad 🔍 CDS (Îą, δ) 🔍 Simbad (Îą, δ)

Overview
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ASCC 20 is a rich, loose object of very high C3 quality. Its parallax locates it at a very close distance, below the mid-plane, affected by low 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 is moderately studied in the literature.

Note: This object shares a large percentage of members with 3 later reported entries. See table with shared members information.

Malhotra et al. (2026)
Lowest/Highest stellar mass in the catalogue with a mass-ratio estimate: 0.17/5.6 Msun

Liu et al. (2025)
Classified as primordial binary cluster 6 along with Briceno_1, and of multiple system 5 along with ASCC_21 and Briceno_1.

Palma et al. (2025)
Part of multiple system G10, along with ASCC_19, OC_0339, OCSN_61 and UBC_17a.

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 ASCC 20 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– 82.08 1.656 2.75 -0.556 0.778 29.188
Malhotra et al. 2026 82.183 1.63 – – – –
Liu et al. 2025 82.19 1.72 2.73 -0.57 0.76 27.89
Yang et al. 2025 82.194 1.721 – – – –
Zhang et al. 2024 82.194 1.721 – – – –
Swiggum et al. 2024 82.194 1.721 2.73 -0.569 0.759 30.108
Hunt & Reffert 2024 82.194 1.721 2.73 -0.569 0.759 27.886
Cavallo et al. 2024 82.006 1.698 2.731 – – –
Hunt & Reffert 2023 82.194 1.721 2.73 -0.569 0.759 27.886
Donor et al. 2020 82.189 1.64 – 1.42 -1.9 19.4
Dib et al. 2018 82.189 1.64 – – – –
Sampedro et al. 2017 82.183 1.63 – 2.15 -3.41 –
Joshi et al. 2016 82.189 1.64 – – – –
Kharchenko et al. 2016 82.183 1.64 – – – –
Dias et al. 2014 82.183 1.63 – 1.85 -3.36 –
Kharchenko et al. 2013 82.189 1.64 – 0.59 0.33 23.0
Gozha et al. 2012 82.183 1.63 – – – –
Piskunov et al. 2008 82.181 1.627 – – – –
Kharchenko et al. 2007 82.18 1.63 – 0.75 – 22.97
Piskunov et al. 2007 82.181 1.627 – – – –
Kharchenko et al. 2005 82.18 1.63 – -0.09 0.51 17.62

💡 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 99999– 0.39 0.13 0.47 13 0.020 649 – –
Malhotra et al. 2026 0.36 0.03 – 25 -0.030 – – –
Liu et al. 2025 0.38 0.06 – 25 – – – –
Yang et al. 2025 – – – 13 -0.070(3) – – –
Zhang et al. 2024 – – – – 0.050(1) – – –
Swiggum et al. 2024 0.36 – – 13 – 161 – –
Hunt & Reffert 2024 0.36 0.11 0.47 13 – 105(1) – –
Cavallo et al. 2024 0.37 0.53 – 13 0.030 – – –
Hunt & Reffert 2023 0.36 0.11 0.47 13 – – – –
Spina et al. 2022 – – – – 0.020 – – –
Donor et al. 2020 – – – – 0.020 – – –
Dib et al. 2018 0.39 – – 10 – – – –
Joshi et al. 2016 0.39 0.20 – 10 – 676 – –
Kharchenko et al. 2016 0.39 0.20 – 10 – – – –
Kharchenko et al. 2013 0.39 0.20 – 10 – – – –
Gozha et al. 2012 0.45 – – 22 – 676 – –
Piskunov et al. 2008 0.45 0.13 – 22 – 1186(1) – –
Piskunov et al. 2007 0.45 0.13 – 22 – 622 – –
Kharchenko et al. 2005 0.45 0.13 – 22 – – – –

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

Cluster % RA DEC Plx pmRA pmDE Rv UTI
OCSN 57 97.1 82.08 1.67 2.74 -0.52 0.79 29.19 0.09
FoF 2371 37.7 82.39 2.02 2.69 -0.68 0.69 29.78 0.1
OCSN 56 17.2 82.64 2.37 2.53 -0.82 0.53 31.28 0.13

💡 Note: The % column shows the percentage of members that ASCC 20 shares with each listed object.

Visualization
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ASCC 20 UCC
ASCC 20 HUNT23
Galactocentric position diagram