Sagittarius A* cluster

The Sagittarius A* cluster is the cluster of stars in close orbit around Sagittarius A*, the supermassive black hole at the center of the Milky Way (in the Galactic Center). The individual stars are often listed as "S-stars", but their names and IDs are not formalized, and stars generally have a different number in different catalogues.

Inferred orbits of 6 stars around supermassive black hole candidate Sagittarius A* at the Milky Way's center[1]

One of the most studied stars is S2, a relatively bright star that also passes close by Sgr A*.

As of 2020, S4714 is the current record holder of closest approach to Sagittarius A*, at about 12.6 astronomical units (1.88×109 km), almost as close as Saturn gets to the Sun, traveling at about 8% of the speed of light. These figures given are approximate, the formal uncertainties being 12.6±9.3 au and 23928±8840 km/s. Its orbital period is 12 years, but an extreme eccentricity of 0.985 gives it the close approach and high velocity.[2]

List of stars

Inferred orbits of stars around supermassive black hole candidate Sagittarius A* at the Milky Way's center according to Gillessen et al. 2017,[3] with the exception of S2 which is from GRAVITY 2019,[4] S62 which is from Peißker et al. Jan 2020,[5] and S4711 up to S4715, which are also from Peißker et al, Aug 2020.[2]

Here id1 is the star's name in the Gillessen catalog and id2 in the catalog of the University of California, Los Angeles. a, e, i, Ω and ω are standard orbital elements, with a measured in arcseconds. Tp is the epoch of pericenter passage, P is the orbital period in years and Kmag is the K-band apparent magnitude of the star. q and v are the pericenter distance in AU and pericenter speed in percent of the speed of light,[6] and Δ indicates the standard deviation of the associated quantities.

id1 id2 a Δa e Δe i (°) Δi Ω (°) ΔΩ ω (°) Δω Tp (yr) ΔTp P (yr) ΔP Kmag q (AU) Δq v (%c) Δv
S1 S0-1 0.5950 0.0240 0.5560 0.0180 119.14 0.21 342.04 0.32 122.30 1.40 2001.800 0.150 166.0 5.8 14.70 2160.7 6.7 0.55 0.03
S2 S0-2 0.1251 0.0001 0.8843 0.0001 133.91 0.05 228.07 0.04 66.25 0.04 2018.379 0.001 16.1 0.0 13.95 118.4 0.2 2.56 0.00
S4 S0-3 0.3570 0.0037 0.3905 0.0059 80.33 0.08 258.84 0.07 290.80 1.50 1957.400 1.200 77.0 1.0 14.40 1779.7 25.1 0.57 0.01
S6 S0-7 0.6574 0.0006 0.8400 0.0003 87.24 0.06 85.07 0.12 116.23 0.07 2108.610 0.030 192.0 0.2 15.40 860.3 4.4 0.94 0.00
S8 S0-4 0.4047 0.0014 0.8031 0.0075 74.37 0.30 315.43 0.19 346.70 0.41 1983.640 0.240 92.9 0.4 14.50 651.7 22.5 1.07 0.01
S9 S0-5 0.2724 0.0041 0.6440 0.0200 82.41 0.24 156.60 0.10 150.60 1.00 1976.710 0.920 51.3 0.7 15.10 793.2 36.9 0.93 0.02
S12 S0-19 0.2987 0.0018 0.8883 0.0017 33.56 0.49 230.10 1.80 317.90 1.50 1995.590 0.040 58.9 0.2 15.50 272.9 2.0 1.69 0.01
S13 S0-20 0.2641 0.0016 0.4250 0.0023 24.70 0.48 74.50 1.70 245.20 2.40 2004.860 0.040 49.0 0.1 15.80 1242.0 2.4 0.69 0.01
S14 S0-16 0.2863 0.0036 0.9761 0.0037 100.59 0.87 226.38 0.64 334.59 0.87 2000.120 0.060 55.3 0.5 15.70 56.0 3.8 3.83 0.06
S17 0.3559 0.0096 0.3970 0.0110 96.83 0.11 191.62 0.21 326.00 1.90 1991.190 0.410 76.6 1.0 15.30 1755.3 16.4 0.57 0.02
S18 S0-18 0.2379 0.0015 0.4710 0.0120 110.67 0.18 49.11 0.18 349.46 0.66 1993.860 0.160 41.9 0.2 16.70 1029.3 3.8 0.77 0.01
S19 S0-28 0.5200 0.0940 0.7500 0.0430 71.96 0.35 344.60 0.62 155.20 2.30 2005.390 0.160 135.0 14.0 16.00 1063.3 4.5 0.83 0.20
S21 0.2190 0.0017 0.7640 0.0140 58.80 1.00 259.64 0.62 166.40 1.10 2027.400 0.170 37.0 0.3 16.90 422.7 3.6 1.32 0.02
S22 1.3100 0.2800 0.4490 0.0880 105.76 0.95 291.70 1.40 95.00 20.00 1996.900 10.200 540.0 63.0 16.60 5903.7 9.7 0.32 0.10
S23 0.2530 0.0120 0.5600 0.1400 48.00 7.10 249.00 13.00 39.00 6.70 2024.700 3.700 45.8 1.6 17.80 910.5 1.6 0.85 0.06
S24 S0-26 0.9440 0.0480 0.8970 0.0049 103.67 0.42 7.93 0.37 290.00 15.00 2024.500 0.030 331.0 16.0 15.60 795.3 30.8 0.99 0.07
S29 0.4280 0.0190 0.7280 0.0520 105.80 1.70 161.96 0.80 346.50 5.90 2025.960 0.940 101.0 2.0 16.70 952.2 67.4 0.87 0.05
S31 S0-8 0.4490 0.0100 0.5497 0.0025 109.03 0.27 137.16 0.30 308.00 3.00 2018.070 0.140 108.0 1.2 15.70 1653.7 14.6 0.63 0.02
S33 S0-33 0.6570 0.0260 0.6080 0.0640 60.50 2.50 100.10 5.50 303.70 1.60 1928.000 12.000 192.0 5.2 16.00 2106.5 179.7 0.56 0.03
S38 S0-38 0.1416 0.0002 0.8201 0.0007 171.10 2.10 101.06 0.24 17.99 0.25 2003.190 0.010 19.2 0.0 17.00 208.4 1.5 1.91 0.01
S39 0.3700 0.0150 0.9236 0.0021 89.36 0.73 159.03 0.10 23.30 3.80 2000.060 0.060 81.1 1.5 16.80 231.2 3.3 1.86 0.09
S42 0.9500 0.1800 0.5670 0.0830 67.16 0.66 196.14 0.75 35.80 3.20 2008.240 0.750 335.0 58.0 17.50 3364.4 24.8 0.44 0.13
S54 1.2000 0.8700 0.8930 0.0780 62.20 1.40 288.35 0.70 140.80 2.30 2004.460 0.070 477.0 199.0 17.50 1050.2 1.9 0.86 0.78
S55 S0-102 0.1078 0.0010 0.7209 0.0077 150.10 2.20 325.50 4.00 331.50 3.90 2009.340 0.040 12.8 0.1 17.50 246.1 4.1 1.70 0.02
S60 0.3877 0.0070 0.7179 0.0051 126.87 0.30 170.54 0.85 29.37 0.29 2023.890 0.090 87.1 1.4 16.30 894.5 1.7 0.89 0.02
S62 0.0897 0.00005 0.9760 0.0020 72.76 4.58 122.61 0.57 42.62 0.40 2003.330 0.010 9.9 0.0 16.10 16.4 1.5 7.03 0.04
S66 S1-2 1.5020 0.0950 0.1280 0.0430 128.50 1.60 92.30 3.20 134.00 17.00 1771.000 38.000 664.0 37.0 14.80 10712.4 620.5 0.21 0.02
S67 S1-3 1.1260 0.0260 0.2930 0.0570 136.00 1.10 96.50 6.40 213.50 1.60 1705.000 22.000 431.0 10.0 12.10 6511.2 360.6 0.29 0.01
S71 S0-71 0.9730 0.0400 0.8990 0.0130 74.00 1.30 35.16 0.86 337.80 4.90 1695.000 21.000 346.0 11.0 16.10 803.8 1.4 0.99 0.06
S83 S0-15 1.4900 0.1900 0.3650 0.0750 127.20 1.40 87.70 1.20 203.60 6.00 2046.800 6.300 656.0 69.0 13.60 7738.6 22.5 0.27 0.05
S85 4.6000 3.3000 0.7800 0.1500 84.78 0.29 107.36 0.43 156.30 6.80 1930.200 9.800 3580.0 2550.0 15.60 8277.1 29.6 0.30 0.33
S87 S1-12 2.7400 0.1600 0.2240 0.0270 119.54 0.87 106.32 0.99 336.10 7.70 611.000 154.000 1640.0 105.0 13.60 17390.5 2572.9 0.17 0.02
S89 1.0810 0.0550 0.6390 0.0380 87.61 0.16 238.99 0.18 126.40 4.00 1783.000 26.000 406.0 27.0 15.30 3191.8 407.2 0.46 0.04
S91 1.9170 0.0890 0.3030 0.0340 114.49 0.32 105.35 0.74 356.40 1.60 1108.000 69.000 958.0 50.0 12.20 10928.4 74.5 0.22 0.02
S96 S0-96 1.4990 0.0570 0.1740 0.0220 126.36 0.96 115.66 0.59 233.60 2.40 1646.000 16.000 662.0 29.0 10.00 10127.0 530.0 0.22 0.02
S97 S1-16 2.3200 0.4600 0.3500 0.1100 113.00 1.30 113.20 1.40 28.00 14.00 2132.000 29.000 1270.0 309.0 10.30 12333.9 305.9 0.21 0.08
S145 1.1200 0.1800 0.5000 0.2500 83.70 1.60 263.92 0.94 185.00 16.00 1808.000 58.000 426.0 71.0 17.50 4580.2 1471.2 0.37 0.10
S175 0.4140 0.0390 0.9867 0.0018 88.53 0.60 326.83 0.78 68.52 0.40 2009.510 0.010 96.2 5.0 17.50 45.0 0.8 4.27 0.47
S4711 0.0751 0.0015 0.768 0.030 114.71 2.92 20.10 3.72 131.59 3.09 2010.85 0.06 7.6 0.3 18.4 143.7 7.4 2.2 0.2
S4712 0.451 0.0025 0.365 0.032 117.28 1.31 166.38 3.20 238.08 3.43 2007.12 0.08 112.0 2.9 18.4 2366 120 0.48 0.02
S4713 0.2 0.095 0.351 0.059 111.07 1.66 95.06 5.15 301.97 8.02 2000.03 0.22 33.2 2.5 18.5 1073 110 0.71 0.05
S4714 0.102 0.0003 0.985 0.011 127.7 0.28 129.28 0.63 357.25 0.08 2017.29 0.02 12.0 0.3 17.7 12.6 9.3 8.0 3
S4715 0.1439 0.011 0.247 0.040 129.8 3.72 282.15 2.92 359.99 5.38 2008.05 0.3 20.2 2.4 17.8 894 83 0.75 0.04
R34 1.8100 0.1500 0.6410 0.0980 136.00 8.30 330.00 19.00 57.00 8.00 1522.000 52.000 877.0 83.0 14.00 5314.6 856.3 0.36 0.05
R44 3.9000 1.4000 0.2700 0.2700 131.00 5.20 80.50 7.10 217.00 24.00 1963.000 85.000 2730.0 1350.0 14.00 23285.6 901.5 0.15 0.11

References
  1. Eisenhauer, F.; et al. (July 20, 2005). "SINFONI in the Galactic Center: Young Stars and Infrared Flares in the Central Light-Month". The Astrophysical Journal. 628 (1): 246–259. arXiv:astro-ph/0502129. Bibcode:2005ApJ...628..246E. doi:10.1086/430667.
  2. Peißker, Florian; Eckart, Andreas; Zajaček, Michal; Basel, Ali; Parsa, Marzieh (August 2020). "S62 and S4711: Indications of a Population of Faint Fast-moving Stars inside the S2 Orbit—S4711 on a 7.6 yr Orbit around Sgr A*". The Astrophysical Journal. 889 (50): 5. arXiv:2008.04764. Bibcode:2020ApJ...899...50P. doi:10.3847/1538-4357/ab9c1c. S2CID 221095771.
  3. Gillessen, S.; et al. (February 2017). "An Update on Monitoring Stellar Orbits in the Galactic Center". The Astrophysical Journal. 837 (1): 30. arXiv:1611.09144. Bibcode:2017ApJ...837...30G. doi:10.3847/1538-4357/aa5c41. S2CID 119087402.
  4. Abuter, R.; Amorim, A.; Bauböck, M.; Berger, J. P.; Bonnet, H.; Brandner, W.; Clénet, Y.; Coudé Du Foresto, V.; De Zeeuw, P. T.; Dexter, J.; Duvert, G.; Eckart, A.; Eisenhauer, F.; Förster Schreiber, N. M.; Garcia, P.; Gao, F.; Gendron, E.; Genzel, R.; Gerhard, O.; Gillessen, S.; Habibi, M.; Haubois, X.; Henning, T.; Hippler, S.; Horrobin, M.; Jiménez-Rosales, A.; Jocou, L.; Kervella, P.; Lacour, S.; et al. (April 2019). "A geometric distance measurement to the Galactic center black hole with 0.3% uncertainty". Astronomy & Astrophysics. 625: L10. arXiv:1904.05721. Bibcode:2019A&A...625L..10G. doi:10.1051/0004-6361/201935656. S2CID 119190574.
  5. Peißker, Florian; Eckart, Andreas; Parsa, Marzieh (January 2020). "S62 on a 9.9 year orbit around SgrA*". The Astrophysical Journal. 889 (1): 61. arXiv:2002.02341. Bibcode:2020ApJ...889...61P. doi:10.3847/1538-4357/ab5afd. S2CID 211043784.
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