Multiple Planet systems

Multiple Planet systems

Several multiple planet systems have been identified. The first, Upsilon Andromedae, is a triple planet system that was discovered by the Lick and AFOE teams in 1999. This announcement has been followed by the detection of several double planet systems.

Double-planet systems include:

  • HD38529 (Lick and Keck)
  • HD12661 (Lick and Keck)
  • HD37124 (Keck Observatory)
  • HD168443 (Keck Observatory)
  • GJ876 (Lick and Keck)
  • HD82943 (Geneva Team)
  • HD74156. (Geneva Team)
  • 47 UMa (Lick Observatory)
  • Triple-planet systems include:
  • Upsilon Andromedae (Lick Observatory, AFOE)
  • New
  • 55 Cnc (Lick Observatory)
  • The long time baseline of observations at Lick Observatory, coupled with high precision, frequent observations make this sample ideal for an investigation of the statistical rate of occurance of multiple planet systems. Fischer et al. established a set of stars on the Lick planet search project that met the following criteria:
      • one known planet
      • at least 2 years of observations
    Twelve stars met these selection criteria. The characteristics of these stars are listed in the table below. After accounting for the velocity variation attributable to the one known planet, we evaluated the residual velocities for evidence of a second trend that could be consistent with Keplerian velocity variations. The residual velocity trends observed in at least half of these stars, suggest that known planet-bearing stars appear to harbor a distant detectable companion more often than other stars in our planet survey.

    starMass (solar)P (days) Msini (Jup)ecc [Fe/H] log R'HK residual trend?
    Tau Boo 1.3 3.31264.140.02 0.32 -4.75yes
    51 Peg 1.06 4.2310.460.01 0.21 -5.03no
    Ups And b 1.3 4.6170.680.02 0.12 -4.842 more
    HD 217107 0.98 7.1281.290.14 0.30 -5.09yes
    55 Cnc 1.0314.6560.930.03 0.45 -4.912 more
    HD 38529 1.4 14.31 0.760.27 0.29 -4.89yes
    HD 195019 1.0218.21 3.560.01 0.00 -4.90no
    Rho Cr B 0.9539.81 0.990.07-0.29 -5.02no
    GJ 876 0.3260.0 2.180.25 N/A N/A yes
    70 Vir 1.10116.7 7.420.40-0.03 -5.06no
    16 CygB 1.02796.7 1.680.680.09 -4.98no
    47 UMa 1.031097.02.630.12-0.08 -4.99 yes

    Most recently updated on 20 April 2003

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