NGC 6633

(Melotte 201; Collinder 380; MWSC 2917; OCL 90; FoF 2425; OCSN 241)

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0.97 UTI
0.87
CN
1.0
Cdens
1.0
CC3
1.0
Clit
1.0
Cdup
Nm (P>50%) 423
Core radius and density 2.1 [pc], 9.6 [pc-2]
C3 classification AA
  • CN 0.87 Rich
  • Cdens 1.0 Very 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¸
NGC 6633 is a rich, very dense object of very high C3 quality. Its parallax locates it at a very 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 age, metallicity, and mass parameters (see Parameters). It is very well-studied in the literature.

Note: This object contains blue stragglers according to at least one source.

Note: This object shares a very small percentage of members with a later reported entry. See table with shared members information.

Malhotra et al. (2026)
Lowest/Highest stellar mass in the catalogue with a mass-ratio estimate: 0.25/2.02 Msun

Yan et al. (2026)
Number of WDs: expected from single-star evolution N=34, with probability of formation through binary evolution >=0.5 N=4.

Palma et al. (2025)
Classified as optical pair P495, along with HSC_295.

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

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).

Richer et al. (2021)
The expected number of WDs is 31.1, 1 WD candidate found, and 0 WD candidates found in the wide search.

Hu et al. (2021)
Ellipticities (core, all): e_core=0.1653, e_all=0.0454.

Rain et al. (2021)
This cluster was include in (Dias et al., 2002A&A...389..871D, Cat. B/ocl) however, parameters log(t)=8.888, Av=0.451, [Fe/H]=-0.080 were taken from Bossini et al. (2019A&A...623A.108B, Cat. J/A+A/623/A108).

Ahumada & Lapasset (2007)
According to the proper motion study (1973A&AS....9..213S), star 32=HD 169959 has a probability membership of 90%, and star 66=HD 170054 has 70%. Star 159=HD 170563 is a cluster member according to (1958ApJ...127..539H). References (1985ApJ...294L.103A), (1974ApJ...194..657H), (1977IBVS.1293....1H), and (1977A&AS...27..117M) cite stars 32 and 159 as blue stragglers. In (1985ApJ...294L.103A) the following spectra and projected velocities are given: star 32, A0III, v.sin i<40km/s; 159, B6IVp(Si), v.sin i<20km/s. Star 66 has a spectrum B6IV (1977PASP...89..274L). Star 155 is HD 170472. Reference (2000A&A...356..517A) also studies spectro- scopically the stragglers 32 and 66.

Data
🔍 Search references for NGC 6633 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– 276.841 6.61 2.538 1.226 -1.824 -28.452
Yan et al. 2026 276.805 6.559 2.54 1.204 -1.804 –
Malhotra et al. 2026 276.876 6.639 – – – –
Nizovkina et al. 2025 276.805 6.559 – – – –
Li et al. 2025 276.845 6.615 2.525 1.198 -1.811 –
Wei et al. 2025 276.821 6.619 2.536 1.216 -1.824 –
Almeida et al. 2025 276.865 6.611 – – – –
Alfonso et al. 2024 276.841 6.641 2.506 1.227 -1.824 –
Zhang et al. 2024 276.805 6.559 – – – –
Hunt & Reffert 2024 276.805 6.559 2.54 1.204 -1.804 -27.901
Cavallo et al. 2024 276.853 6.647 2.538 – – –
Hunt & Reffert 2023 276.805 6.559 2.54 1.204 -1.804 -27.901
Almeida et al. 2023 276.865 6.641 – – – –
Qin et al. 2023 276.85 6.65 2.54 1.24 -1.81 -28.49
Just et al. 2023 276.829 6.499 – – – –
He et al. 2022 276.846 6.607 2.539 1.224 -1.808 –
Tarricq et al. 2022 276.791 6.786 2.545 1.237 -1.813 –
Jadhav & Subramaniam 2021 276.845 6.615 – – – –
Jaehnig et al. 2021 276.861 6.611 2.551 1.202 -1.808 –
Netopil et al. 2022 276.812 6.508 – – – -29.1
Rain et al. 2021 276.845 6.615 2.525 1.198 -1.811 –
Richer et al. 2021 276.855 6.554 2.529 1.11 -1.755 –
Dias et al. 2021 276.865 6.611 2.518 1.195 -1.795 -28.195
Cantat-Gaudin et al. 2020 276.845 6.615 2.525 1.198 -1.811 –
Zhong et al. 2020 276.845 6.615 – 1.198 -1.811 -40.75
Cantat-Gaudin & Anders 2020 276.845 6.615 2.525 1.198 -1.811 –
Liu & Pang 2019 276.876 6.629 2.514 1.2 -1.775 –
Bossini et al. 2019 276.845 6.615 – – – –
Soubiran et al. 2018 276.845 6.615 – – – -28.62
Bica et al. 2019 276.935 6.556 – – – –
Cantat-Gaudin et al. 2018 276.845 6.615 2.525 1.198 -1.811 –
Dib et al. 2018 276.835 6.5 – – – –
Loktin & Popova 2017 276.81 6.508 – -3.982 -5.701 -25.4
Sampedro et al. 2017 276.812 6.508 – -2.77 -5.83 –
Joshi et al. 2016 276.835 6.5 – – – –
Kharchenko et al. 2016 276.829 6.499 – – – –
Netopil et al. 2016 276.88 6.57 – – – –
Dias et al. 2014 276.813 6.508 – -2.27 -4.95 –
Kharchenko et al. 2013 276.835 6.5 – -0.3 -2.65 -25.4
Gozha et al. 2012 276.812 6.508 – – – –
Piskunov et al. 2008 276.801 6.513 – – – –
Kharchenko et al. 2007 276.81 6.51 – 0.51 – -25.43
Piskunov et al. 2007 276.801 6.513 – – – –
Ahumada & Lapasset 2007 276.825 6.517 – – – –
van den Bergh 2006 276.88 6.57 – – – –
Kharchenko et al. 2005 276.81 6.51 – 0.1 -2.0 -25.43
Kharchenko et al. 2003 276.87 6.54 – -0.16 -2.51 –
Chen et al. 2003 276.877 6.574 – -0.01 -0.51 -29.1
Dias et al. 2002 276.812 6.508 – -2.27 -4.95 -28.95
Lynga 1987 276.891 6.557 – – – -28.0
Sulentic et al. 1973 276.88 6.566 – – – –

💡 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 0.56 0.96 575 -0.066 196 0.58 1
Yan et al. 2026 – – – 691 – – – –
Malhotra et al. 2026 0.39 0.29 – 855 -0.043 – – –
Nizovkina et al. 2025 0.35(4) 0.52(4) – 791(4) -0.168(4) – – –
Li et al. 2025 0.38 0.54 – 759 -0.052 – – –
Wei et al. 2025 0.50 0.68 – 417 0.250 653 0.45 –
Almeida et al. 2025 0.39 0.77 – 607 – 265 – –
Alfonso et al. 2024 0.42 0.30 – 1142 -0.092 – – –
Zhang et al. 2024 – – – – -0.148(1) – – –
Hunt & Reffert 2024 0.37 0.39 0.96 472 – 574(1) – –
Cavallo et al. 2024 0.39 0.84 – 331 0.130 – – –
Hunt & Reffert 2023 0.37 0.39 0.96 472 – – – –
Almeida et al. 2023 0.39 0.55 – 796 -0.117 512(1) 0.71 –
Qin et al. 2023 0.48 0.54 – 708 – – – –
Just et al. 2023 – – – 575 – 14 – –
He et al. 2022 – 0.85 – 447 – – – –
Spina et al. 2022 – – – – -0.084 – – –
Tarricq et al. 2022 0.42 – – 708 – – – –
Jadhav & Subramaniam 2021 0.42 0.30 – 692 – 367 – 1(1)
Jaehnig et al. 2021 0.39(1) – – – – – – –
Netopil et al. 2022 0.42(1) – – 692 -0.020(1) – – –
Rain et al. 2021 0.39 0.57 – 417 – – – 1
Richer et al. 2021 – 0.59 – 692 – – – –
Dias et al. 2021 0.39 0.77 – 607 -0.094 – – –
Cantat-Gaudin et al. 2020 0.42 0.30 – 692 – – – –
Kounkel et al. 2020 0.41 0.41 – 631 – – – –
Zhong et al. 2020 0.39(1) 0.46 – 8888 -0.104 – – –
Cantat-Gaudin & Anders 2020 0.39 – – – – – – –
Liu & Pang 2019 – – – 501 0.500 – – –
Bossini et al. 2019 0.37 0.45 – 773 -0.080 – – –
Soubiran et al. 2018 0.39 – – – – – – –
Cantat-Gaudin et al. 2018 0.39 – – – – – – –
Dib et al. 2018 0.39 – – 575 – – – –
Loktin & Popova 2017 0.41 0.56 – 471 – – – –
Joshi et al. 2016 0.39 0.56 – 575 – 126 – –
Kharchenko et al. 2016 0.39 0.56 – 575 – – – –
Netopil et al. 2016 7.72 – – 520 -0.080(2) – – –
Heiter et al. 2014 – – – – -0.080 – – –
Kharchenko et al. 2013 0.39 0.56 – 575 0.060 – – –
Gozha et al. 2012 0.38 – – 426 0.060 126 – –
Paunzen et al. 2010 – – – – -0.050 – – –
Piskunov et al. 2008 0.39 0.57 – 575 – 109(1) – –
Piskunov et al. 2007 0.39 0.57 – 575 – 29 – –
Ahumada & Lapasset 2007 – 0.57 – 427 – – – 4
van den Bergh 2006 0.38 0.57 – 427 – – – –
Kharchenko et al. 2005 0.39 0.57 – 575 – – – –
Kharchenko et al. 2003 0.38 0.57 – – – – – –
Chen et al. 2003 0.38 0.57 – 420 0.000(1) – – –
Dias et al. 2002 0.38 0.57 – 426 0.060 – – –
Lynga 1987 0.32 0.54 – 661 -0.110 – – –

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

Cluster % RA DEC Plx pmRA pmDE Rv UTI
OC 0067 9.7 277.0 6.72 2.54 1.31 -1.69 -28.71 0.0

💡 Note: The % column shows the percentage of members that NGC 6633 shares with each listed object.

Visualization
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NGC 6633 UCC
NGC 6633 HUNT23
NGC 6633 CANTAT20
Galactocentric position diagram