HD 74156

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HD 74156
Observation data
Epoch 2000
Constellation
(pronunciation)		 Hydra
Right ascension 08h 42m 25.1222s
Declination +04° 34' 41.151"
Apparent magnitude (V) 7.62
Distance 210.6 ly
(64.56 pc)
Spectral type G0V
Other designations
BD+05°2035, HIP 42723

HD 74156 is a yellow dwarf star (spectral type G0V) in the constellation of Hydra, 210 light years from our solar system. It is known to be orbited by three large planets.

Contents

[edit] Planets

[edit] HD 74156 b

HD 74156 b
Extrasolar planet List of extrasolar planets
Orbital elements
Semimajor axis (a) 0.294 AU
Eccentricity (e) 0.64±0.01
Orbital period (P) 51.65±0.01 d
Angular distance (θ) 5 mas
Longitude of
periastron		 (ω) 175.8±1.4°
Time of periastron (T0) 2,451,980.8±0.1 JD
Semi-amplitude (K) 112±1.9 m/s
Physical characteristics
Mass (m) >1.88±0.03 MJ
Discovery information
Discovery date Apr 4, 2001
Discoverer(s) Naef, Mayor et al.
Detection method Radial velocity
Discovery site California
Discovery status Published

HD 74156 b is an extrasolar planet at least 88% more massive than Jupiter that orbits very close to the star. Its surface temperatures must be high and its radius about 1.1 to 1.3 that of Jupiter. It is most likely a gas giant.

[edit] HD 74156 c

HD 74156 c
Extrasolar planet List of extrasolar planets
Orbital elements
Semimajor axis (a) 3.85 AU
Eccentricity (e) 0.43±0.01
Orbital period (P) 2476±8.7 d
Angular distance (θ) 60 mas
Longitude of
periastron		 (ω) 261.3±2°
Time of periastron (T0) 2,450,952.2±13.8 JD
Semi-amplitude (K) 130.3 m/s
Physical characteristics
Mass (m) >8.03±0.12 MJ
Discovery information
Discovery date Apr 4, 2001
Discoverer(s) Naef, Mayor et al.
Detection method Radial velocity
Discovery site California
Discovery status Published

HD 74156 c is an extrasolar planet at least eight times the mass of Jupiter but likely to be smaller than the innermost planet (roughtly Jupiter's size), with an eccentric orbit that occasionally passes through the star's habitable zone. It would thus be subject to extreme shifts of temperature. It is most likely a gas giant.

[edit] HD 74156 d

HD 74156 d
Extrasolar planet List of extrasolar planets
Orbital elements
Semimajor axis (a) 1.04 AU
Eccentricity (e) 0.25±0.11
Orbital period (P) 346.6±3.6 d
Angular distance (θ) 16 mas
Longitude of
periastron		 (ω) 166.5±27.4°
Time of periastron (T0) 2,450,678.2±44.2 JD
Semi-amplitude (K) 29.8 m/s
Physical characteristics
Mass (m) >0.4±0.02 MJ
Discovery information
Discovery date Sept 11, 2007
Discoverer(s) Bean et al.
Detection method Radial velocity
Discovery site Texas
Discovery status Published

HD 74156 d is a gas giant 40% the mass of Jupiter. It orbits about the same distance as Earth to the Sun, this puts it in the star's habitable zone. It was first observed by Jacob Bean and his team at the University of Texas.

The existence of HD 74156 d was predicted by computer models created by Rory Barnes, Thomas Quinn and Sean Raymond, operating under the theory that planetary systems would have planets occupying every stable orbital zone. The two previously discovered planets of this system left a stable gap between them where HD 74156 d was ultimately detected. This was the first extrasolar planet whose existence was predicted by theory before it was detected experimentally.[1]

However, doubts have subsequently been raised about whether HD 74156 d has actually been detected; Roman V. Baluev suggests its observed effects may be explained by errors in the data.[2]

[edit] See also

[edit] References

  1. ^ Centauri Dreams » Blog Archive » Exoplanet Prediction Confirmed
  2. ^ Accounting for velocity jitters in planet search surveys by Roman V. Baluev

[edit] External links

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