The Orbital Elements of selected visual binaries


The binaries are arranged by constellation. The seven orbital elements allow one to calculate the position of a companion to its primary, for any desired date. The process isn't terribly difficult, and is found in Peter Duffett-Smith's Practical Astronomy With Your Calculator. The given positions ("ephemerides") are those for 1 January 2000.

The Orbital Elements columns contain the following information:

  1. Constellation: the list contains 26 different constellations.
  2. Star: the star's name. If a link, it contains a drawn orbit.
  3. ADS: the reference number as found in the Aitken Double Star catalogue.
  4. P: the period, that is, the number of years for the companion to make a complete revolution.
    [This entry, and the next six, constitute the "orbital elements"]
    If an asterisk (*) is in the "P" column, the orbit has been recently revised and the latest element values are used.
  5. T: the epoch of periastron.
  6. a: the semimajor axis of the orbit (arcsecs).
  7. e: the eccentricity.
  8. i: the inclination of the orbit.
  9. w: the longitude of the periastron.
  10. W: the position angle of the ascending node.
  11. Ephemerides: the position of the companion in the year 2000. Any separation over 1.0" is generally visible to medium-powered telescopes. Less than that may be difficult to resolve.

    There are five basic factors for resolving binaries:

  • the distance between the two components;
  • the size of a telescope's objective;
  • the apparent magnitudes of the stars in question;
  • the condition of the atmosphere;
  • the skills of the observer.


    Visual Binaries: the orbital elements

    Constellation Star ADS P T a e i w W Ephemerides
    Andromeda Groombridge 34 246 2600 1745 41.15 0.0 61.4 0.0 45.3 2000: 64, 36.3"
    " Struve 73 755 164.7 1957.15 1.014 0.31 46.4 4.65 171.5 2000: 313, 0.9"
    " Gamma2 1630 61.1 1952.1 0.296 0.93 111.1 171.15 104.15 2000: 103, 0.4"
    " Struve 3050 17149 350* 2037.0 3.19 0.51 67 50 353.2 2000: 332, 1.9"
    Aquarius Zeta2-Zeta1 15971 760* 1968.0 4.507 0.50 135.87 63.42 304.64 2000: 198, 2.0"
    Bootes Struve 1785 9031 155.75* 1916.75 2.433 0.446 47.4 200.0 155.4 2000: 173, 3.3"
    " Zeta 9343 123.44 1897.59 0.595 0.9572 142.0 1.47 129.99 2000: 300, 0.8"
    " Xi 9413 151.505 1909.361 4.904 0.512 140.04 203.92 348.1 2000: 318, 6.6"
    " Struve 1909 9494 220* 2017 3.70 0.451 83.7 37.5 57.7 2000: 54, 2.2"
    " Mu2BC 9626 246.04* 1864.5 1.40 0.570 136.6 338.5 176.0 2000: 7, 2.1"
    Cancer ZetaAB 6650 59.50* 1989.23 0.880 0.325 165 204 30.4 2000: 83, 0.8"
    " ZetaABxC 6650 1115* 1970 7.70 0.24 146.0 345.5 74.2 2000: 73, 5.9"
    Canes Venatici Struve 1768 8974 240 1863.95 1.091 0.83 144 137.9 67 2000: 99, 1.8"
    Canis Major Alpha 5423 50.09 1894.13 7.5 0.592 136.53 147.27 44.57 2000: 150, 4.6"
    Cassiopeia Struve 3062 61 106.83 1943.05 1.432 0.45 44.4 278.8 219.1 2000: 328, 1.5"
    Centaurus AlphaAB -- 79.92 1955.56 17.583 0.516 79.24 231.56 204.87 2000: 222, 14.2"
    " Gamma -- 84.50 1931.22 0.93 0.79 112.9 187.8 2.4 2000: 347, 1.0"
    Cepheus Xi 15600 3800 1750 11.5 0.24 109 114 85 2000: 275, 8.2"
    " Kruger 60 15972 44.67* 1970.22 2.383 0.41 167.2 211.0 154.5 2000: 95, 3.0"
    Cetus β395 520 25 1924 0.67 0.22 78 142 112 2000: 289, 0.5"
    " Struve 186 1538 170.3 1893.35 1.05 0.71 73.6 220.7 40.4 2000: 60, 1.1"
    Coma Berenices Struve 1639 8539 678 1891 1.3 0.95 161 334 105.7 2000: 327, 1.6"
    Corona Australis h5014 -- 191.2 1841.68 1.062 0.52 145.2 190.4 49.2 2000: 346, 0.9"
    Corona Borealis Eta 9617 41.56 1892.39 0.839 0.28 58.9 219.6 24.2 2000: 65, 0.7"
    " Sigma 9979 1000 1828 6.599 0.78 33.3 84.35 7.7 2000: 237, 7.1"
    Cygnus Delta 12880 827.6 1885.8 3.2 0.49 147 134 98.7 2000: 222, 2.5"
    " 61 14636 653.34 1676.94 24.307 0.4002 55.01 147.03 171.4 2000: 150, 30.3"
    " Tau 14787 49.9 1939.6 0.88 0.25 134.2 119 159.7 2000: 306, 0.8"
    " Mu 15270 789* 1958.0 5.32 0.66 75.5 145.7 110.1 2000: 308, 1.8"
    Delphinus Beta 14073 26.65 1962.72 0.475 0.35 63.6 346.4 178.6 2000: 343, 0.5"
    Draco 20 10279 729.35 1853.5 1.38 0.466 97 220.3 66.2 2000: 68, 1.4"
    " Mu 10345 672* 1949 3.945 0.45 144.7 197.0 282.8 2000: 18, 2.2"
    " 26 10660 76 1950.4 1.52 0.16 105.7 322 152 2000: 331, 1.7"
    Eridanus Omicron2BC 3093 251.988 1848.872 7.0453 0.4147 108.54 326.497 150.96 2000: 336, 9.3"
    " p -- 483.66 1813.494 7.8169 0.53444 142.82 18.374 13.116 2000: 191, 11.5"
    Fornax Alpha 2402 314 1947 4.37 0.76 81.5 42 117.7 2000: 299, 5.1"
    Gemini Alpha 6175 467* 1958.0 6.805 0.343 114.5 249.5 41.3 2000: 65, 3.9"
    " Delta 5983 1200 1487 6.975 0.11 63.28 57.19 18.4 2000: 225, 5.8"
    " 38 5559 3190 1636 9.55 0.48 148.4 310.5 185.6 2000: 144, 7.1"
    Hercules Alpha 10418 3600 3635 4.68 0 155.8 180 119.6 2000: 104, 4.6"
    " Zeta 10157 34.45* 1967.78 1.365 0.464 131.6 291.9 229.2 2000: 12, 0.73"
    " 99 11077 55.8 1941.8 1.00 0.74 32.0 300.6 218.7 2000: 250, 0.5"
    Hydra EpsilonABxC 6953 990* 1920 4.66 0.30 39 200 49.3 2000: 298, 2.9"
    " β411 7846 210.1 1948.23 0.9824 0.80 126.1 35.8 144.8 2000: 315, 1.4"
    Leo Gamma1 7724 618.6 1743.32 2.505 0.84 36.4 162.5 143.2 2000: 125, 4.4"
    " Iota 8148 192 1948.47 1.92 0.55 130.5 140 52.2 2000: 116, 1.7"
    Lupus Gamma -- 147 1887 0.59 0.49 95.6 301 92.8 2000: 274, 0.7"
    Lynx 12 5400 699 1740 1.66 0.03 180 154.8 0 2000: 69, 1.7"
    " Struve 1338 7307 289.05* 1996.77 1.459 0.61 47.8 252.9 91.5 2000: 289, 1.0"
    " Kui 37 -- 21.80* 1971.91 0.638 0.149 132.5 212.0 24.5 2000: 45, 0.6"
    Lyra Epsilon1AB 11635 1165 1152.4 2.78 0.19 138 165.7 29 2000: 350, 2.6"
    " Epsilon2CD 11635 585 1644.5 2.95 0.49 120.5 88 17.4 2000: 82, 2.3"
    " β648 11871 61.15* 1972.35 1.262 0.258 114.8 283.6 48.13 2000: 317, 0.7"
    Musca Beta -- 383.12 1872.29 1.735 0.526 61.3 98.32 161.81 2000: 43, 1.3"
    Ophiuchus Eta 10374 88 1936.8 0.86 0.84 100.4 279.8 41.4 2000: 244, 0.6"
    " Lambda 10087 129.87 1939.54 0.97 0.618 26.8 158.9 52.5 2000: 30, 1.5"
    " Tau 11005 280 1829 1.494 0.72 59.3 49.78 63 2000: 284, 1.7"
    " 36 10417 548.7 1643.48 13.91 0.9 99.2 90 93.6 2000: 147, 4.9"
    " 70 11046 88.30* 1984.30 4.560 0.495 120.8 13.2 301.4 2000: 149, 3.7"
    Orion Zeta 4263 1509 2070.6 2.728 0.07 72 47.3 155.5 2000: 165, 2.3"
    Pegasus 37 15988 140 1908 0.75 0.51 89 202.3 117.2 2000: 118, 0.7"
    " 85 17175 26.27 1910.11 0.83 0.38 50 94.4 288.6 2000: 184, 0.7"
    Pisces Alpha 1615 933.05 2098.64 4 0.696 120.9 225.4 23.3 2000: 272, 1.8"
    Puppis β101 6420 23.30* 1915.71 0.58 0.69 77.8 67.7 103.3 2000: 331, 0.25"
    Scorpius Alpha 10074 878 1461 2.9 0.1 90 0 93.7 2000: 274, 2.6"
    " Xi 9909 45.69 1951.14 0.72 0.74 36.9 348.2 201.7 2000: 308, 0.4"
    Sculptor Epsilon 1394 1192 2076.2 4.652 0 180 0 0 2000: 23, 4.7"
    " Tau -- 1875.6 1968.6 12.395 0.9832 77.82 85.39 138 2000: 340, 2.1"
    Serpens Delta 9701 3168 1700 6.02 0.31 112.6 274.6 166.8 2000: 176, 4.4"
    Taurus 80 3264 189.5 1888 1.01 0.83 108 162 12.8 2000: 17, 1.8"
    " Struve 422 2644 2101 1900 8.023 0.18 32.1 152 92 2000: 269, 6.7"
    Ursa Major Xi 8119 59.84 1935.17 2.53 0.414 122.65 127.53 101.59 2000: 273, 1.8"
    " Sigma2 7203 1067 1917.7 6.2 0.81 146.2 331.5 99.7 2000: 354, 3.9"
    " β1082 8739 115.7 1921.74 1.256 0.44 51.5 301 269.2 2000: 69, 1.5"
    Vela Psi -- 33.99 1935.75 0.795 0.44 58.5 48.4 287.2 2000: 264, 0.5"
    Virgo Gamma 8630 168.68 2005.13 3.697 0.885 148.0 256.5 36.9 2000: 260, 1.45"
    Vulpecula Struve 2525 12447 990 1887.9 1.97 0.93 133.7 8.5 103.1 2000: 291, 2.1"

    Last updated 16 May 2001

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