Alessi 2

(MWSC 419; LeDrew 4)

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0.93 UTI
0.82
CN
0.85
Cdens
1.0
CC3
1.0
Clit
1.0
Cdup
Nm (P>50%) 287
Core radius and density 2.1 [pc], 4.2 [pc-2]
C3 classification AA
  • CN 0.82 Rich
  • Cdens 0.85 Dense
  • CC3 1.0 Very high quality
  • Clit 1.0 Very well-studied
  • Cdup 1.0 Unique
đŸ“Ĩ Members 📊 Colab đŸ”Ŧ Bayestar19 MOCAMOCA 🔍 CDS 🔍 Simbad 🔍 CDS (Îą, δ) 🔍 Simbad (Îą, δ)

Overview
ℹī¸
Alessi 2 is a rich, dense object of very high C3 quality. Its parallax locates it at a close distance, above 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 metallicity and mass parameters (see Parameters). It is very well-studied in the literature.

Palma et al. (2025)
Classified as optical pair P258, along with Theia_1040.

Almeida et al. (2025)
Mass determination: good fit. Isochrone match: good fit.

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).

Hu et al. (2021)
Ellipticities (core, all): e_core=0.2799, e_all=0.4225.

Piecka & Paunzen (2021)
Belongs to cluster aggregate 'Agg04' along with UPK 312.

Bica et al. (2019)
Web updates in DAML02, some were later removed (2003 to 2010). List of clusters and alike reported by B. Alessi.

Data
🔍 Search references for Alessi 2 in: SciX Simbad
ℹī¸
Reference Year RA [deg] DEC [deg] Plx [mas] pmRA [mas/yr] pmDE [mas/yr] Rv [km/s]
UCC 99999– 71.607 55.181 1.615 -0.915 -1.095 -10.442
Otto et al. 2026 71.557 55.184 – -0.9 -1.05 -10.1
Li et al. 2025 71.602 55.199 1.589 -0.904 -1.046 –
Yang et al. 2025 71.557 55.184 – – – –
Almeida et al. 2025 71.627 55.234 – – – –
Alfonso et al. 2024 71.619 55.181 1.583 -0.925 -1.099 –
Zhang et al. 2024 71.557 55.184 – – – –
Hunt & Reffert 2024 71.557 55.184 1.618 -0.928 -1.095 -10.275
Cavallo et al. 2024 71.648 55.186 1.623 – – –
Hunt & Reffert 2023 71.557 55.184 1.618 -0.928 -1.095 -10.275
Almeida et al. 2023 71.511 55.213 – – – –
Just et al. 2023 71.552 55.255 – – – –
He et al. 2022 71.606 55.2 1.624 -0.944 -1.091 –
Jadhav & Subramaniam 2021 71.602 55.199 – – – –
Dias et al. 2021 71.627 55.234 1.582 -0.896 -1.055 -10.466
Cantat-Gaudin et al. 2020 71.602 55.199 1.589 -0.904 -1.046 –
Zhong et al. 2020 71.602 55.199 – -0.904 -1.046 -20.564
Cantat-Gaudin & Anders 2020 71.602 55.199 1.589 -0.904 -1.046 –
Bossini et al. 2019 71.602 55.199 – – – –
Soubiran et al. 2018 71.602 55.199 – – – -11.0
Bica et al. 2019 71.561 55.234 – – – –
Cantat-Gaudin et al. 2018 71.602 55.199 1.589 -0.904 -1.046 –
Dias et al. 2018 – – – 0.56 -2.7 –
Dib et al. 2018 71.565 55.255 – – – –
Loktin & Popova 2017 71.505 55.207 – 1.62 -3.654 –
Sampedro et al. 2017 71.508 55.207 – 2.31 0.86 –
Joshi et al. 2016 71.565 55.255 – – – –
Kharchenko et al. 2016 71.552 55.255 – – – –
Dias et al. 2014 71.508 55.207 – 1.75 0.14 –
Kharchenko et al. 2013 71.565 55.255 – -0.91 -0.75 –
Kharchenko et al. 2012 71.565 55.255 – -0.91 -0.75 –
Piskunov et al. 2008 71.548 55.228 – – – –
Piskunov et al. 2007 71.548 55.228 – – – –
van den Bergh 2006 71.6 55.25 – – – –
Kharchenko et al. 2005 71.56 55.23 – -0.08 0.31 –
Alessi et al. 2003 71.6 55.25 – 0.2 -1.1 –
Dias et al. 2002 71.508 55.207 – 0.25 -1.09 –

💡 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– 0.59 0.57 0.75 388 -0.015 173 0.54 0
Otto et al. 2026 – – – 355 0.050(15) – – –
Li et al. 2025 0.58 0.68 – 538 -0.029 – – –
Yang et al. 2025 – – – 263 -0.110(3) – – –
Almeida et al. 2025 0.61 0.81 – 396 – 391 – –
Alfonso et al. 2024 0.66 0.52 – 701 0.058 – – –
Zhang et al. 2024 – – – – -0.046(1) – – –
Hunt & Reffert 2024 0.59 0.57 0.75 264 – 289(1) – –
Cavallo et al. 2024 0.62 0.89 – 251 0.270 – – –
Hunt & Reffert 2023 0.59 0.57 0.75 264 – – – –
Almeida et al. 2023 0.60 0.92 – 318 -0.086 317(1) 0.54 –
Just et al. 2023 – – – 499 – 28 – –
He et al. 2022 – 0.85 – 282 – – – –
Tarricq et al. 2022 0.65 – – 380 – – – –
Jadhav & Subramaniam 2021 0.66 0.52 – 355 – 515 – 0(1)
Dias et al. 2021 0.61 0.81 – 396 0.057 – – –
Cantat-Gaudin et al. 2020 0.66 0.52 – 355 – – – –
Kounkel et al. 2020 0.62 0.78 – 195 – – – –
Zhong et al. 2020 0.62(1) 0.49 – 8759 -0.045 – – –
Cantat-Gaudin & Anders 2020 0.62 – – – – – – –
Bossini et al. 2019 0.59 0.48 – 574 0.000 – – –
Soubiran et al. 2018 0.62 – – – – – – –
Cantat-Gaudin et al. 2018 0.62 – – – – – – –
Dib et al. 2018 0.52 – – 499 – – – –
Loktin & Popova 2017 0.57 0.97 – 34 – – – –
Joshi et al. 2016 0.52 0.47 – 499 – 45 – –
Kharchenko et al. 2016 0.52 0.47 – 499 – – – –
Kharchenko et al. 2013 0.52 0.47 – 499 – – – –
Kharchenko et al. 2012 0.52 0.47 – 499 – – – –
Piskunov et al. 2008 0.50 0.57 – 398 – 57(1) – –
Piskunov et al. 2007 0.50 0.57 – 398 – 10 – –
van den Bergh 2006 0.50 0.57 – 316 – – – –
Kharchenko et al. 2005 0.50 0.57 – 398 – – – –
Alessi et al. 2003 0.50 0.57 – 316 – – – –
Dias et al. 2002 0.50 0.57 – 316 – – – –

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

Visualization
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Alessi 2 UCC
Alessi 2 HUNT23
Alessi 2 CANTAT20
Galactocentric position diagram