HD 74156

Coordinates: Sky map 08h 42m 25.1222s, +04° 34′ 41.151″
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HD 74156
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Hydra
Right ascension 08h 42m 25.12195s[1]
Declination +04° 34′ 41.1457″[1]
Apparent magnitude (V) +7.614[2]
Spectral type G0V
U−B color index ?
B−V color index 0.581[2]
V−R color index 0.4
R−I color index 0.2
Variable type “None”
Radial velocity (Rv)3.90±0.13[1] km/s
Proper motion (μ) RA: 24.666±0.025 mas/yr[1]
Dec.: −200.238±0.019 mas/yr[1]
Parallax (π)17.4242 ± 0.0247 mas[1]
Distance187.2 ± 0.3 ly
(57.39 ± 0.08 pc)
Absolute magnitude (MV)+3.57 ± 0.15
Mass1.24[2] M
Radius1.64 ± 0.19[2] R
Luminosity (bolometric)3.037 ± 0.485[2] L
Surface gravity (log g)4.4 ± 0.15[2] cgs
Temperature5960 ± 100[2] K
Metallicity [Fe/H]+0.13[2] dex
Rotational velocity (v sin i)4.3[2] km/s
Age3.7 ± 0.4[2] Gyr
Other designations
HIP 42723, SAO 117040, BD+05 2035, 2MASS J08422511+0434411
Database references

HD 74156 is a yellow dwarf star (spectral type G0V) in the constellation of Hydra, 187 light years from the Solar System.[1] It is known to be orbited by two giant planets.


This star is 24% more massive and 64% larger than the Sun. The total luminosity is 2.96 times that of the Sun and its temperature 5960 K.[2] The age of the star is estimated at 3.7 billion years,[2] with metallicity 1.35 times that of the Sun based on its abundance of iron.

Planetary system[edit]

In April 2001, two giant planets were announced orbiting the star.[3][4] The first planet HD 74156 b orbits the star at a distance closer than Mercury is to the Sun, in an extremely eccentric orbit. The second planet HD 74156 c is a long-period, massive planet (at least 8 times the mass of Jupiter), which orbits the star in an elliptical orbit with a semimajor axis of 3.90 astronomical units.[2] In 2022, the inclination and true mass of HD 74156 c were measured via astrometry.[5]

The HD 74156 planetary system[6][5]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b ≥1.778±0.020 MJ 0.2916±0.0033 51.6385±0.0015 0.6380±0.0061
c 8.665+1.385
2448.5±4.2 0.377±0.006 120.162+7.601

Claims of a third planet[edit]

Given the two-planet configuration of the system under the assumption that the orbits are coplanar and have masses equal to their minimum masses, an additional Saturn-mass planet would be stable in a region between 0.9 and 1.4 AU between the orbits of the two known planets.[7] Under the "packed planetary systems" hypothesis, which predicts that planetary systems form in such a way that the system could not support additional planets between the orbits of the existing ones, the gap would be expected to host a planet.

In September 2007, a third planet with a mass at least 0.396 Jupiter masses was announced to be orbiting between planets b and c with an eccentric orbit.[8] The planet, orbiting in a region of the planetary system previously known to be stable for additional planets, was seen as a confirmation of the "packed planetary systems" hypothesis.[9] However, Roman V. Baluev has cast doubt on this discovery, suggesting that the observed variations may be due to annual errors in the data.[10] A subsequent search using the Hobby-Eberly Telescope also failed to confirm the planet,[11] and further data obtained using HIRES instrument strongly contradicts its existence.[2]

See also[edit]


  1. ^ a b c d e f Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ^ a b c d e f g h i j k l m n Meschiari, Stefano; et al. (2011). "The Lick-Carnegie Survey: Four New Exoplanet Candidates". The Astrophysical Journal. 727 (2). 117. arXiv:1011.4068. Bibcode:2011ApJ...727..117M. doi:10.1088/0004-637X/727/2/117. S2CID 59065004.
  3. ^ "Exoplanets: The Hunt Continues!" (Press release). Garching, Germany: European Southern Observatory. April 4, 2001. Retrieved December 27, 2012.
  4. ^ Naef, Dominique; Mayor, Michel; Beuzit, Jean-Luc; Perrier, Christian; Queloz, Didier; Sivan, Jean-Pierre; Udry, Stéphane (2004). "The ELODIE survey for northern extra-solar planets. III. Three planetary candidates detected with ELODIE" (PDF). Astronomy and Astrophysics. 414 (1): 351–359. arXiv:astro-ph/0310261. Bibcode:2004A&A...414..351N. doi:10.1051/0004-6361:20034091. S2CID 16603563.
  5. ^ a b Feng, Fabo; Butler, R. Paul; et al. (August 2022). "3D Selection of 167 Substellar Companions to Nearby Stars". The Astrophysical Journal Supplement Series. 262 (21): 21. arXiv:2208.12720. Bibcode:2022ApJS..262...21F. doi:10.3847/1538-4365/ac7e57. S2CID 251864022.
  6. ^ Feng, Y. Katherina; et al. (2015). "The California Planet Survey IV: A Planet Orbiting the Giant Star HD 145934 and Updates to Seven Systems with Long-period Planets". The Astrophysical Journal. 800 (1). 22. arXiv:1501.00633. Bibcode:2015ApJ...800...22F. doi:10.1088/0004-637X/800/1/22. S2CID 56390823.
  7. ^ Sean N. Raymond; Rory Barnes (2005). "Predicting Planets in Known Extrasolar Planetary Systems. II. Testing for Saturn Mass Planets". The Astrophysical Journal. 619 (1): 549–557. arXiv:astro-ph/0404211. Bibcode:2005ApJ...619..549R. doi:10.1086/426311. S2CID 13015545.
  8. ^ Jacob L. Bean; et al. (2008). "Detection of a Third Planet in the HD 74156 System Using the Hobby-Eberly Telescope". The Astrophysical Journal. 672 (2): 1202–1208. arXiv:0709.1656. Bibcode:2008ApJ...672.1202B. doi:10.1086/523701. hdl:2152/35107. S2CID 15507937.
  9. ^ Barnes, Rory; et al. (2008). "The Successful Prediction of the Extrasolar Planet HD 74156 d". The Astrophysical Journal Letters. 680 (1): L57–L60. arXiv:0804.4496. Bibcode:2008ApJ...680L..57B. doi:10.1086/589712. S2CID 14070540.
  10. ^ Baluev, Roman V. (2008). "Accounting for velocity jitters in planet search surveys". Monthly Notices of the Royal Astronomical Society. 393 (3): 969–978. arXiv:0712.3862. Bibcode:2009MNRAS.393..969B. doi:10.1111/j.1365-2966.2008.14217.x. S2CID 15170720.
  11. ^ Wittenmyer, Robert A.; Endl, Michael; Cochran, William D.; Levison, Harold F.; Henry, Gregory W. (2009). "A Search for Multi-Planet Systems Using the Hobby-Eberly Telescope". The Astrophysical Journal Supplement. 182 (1): 97–119. arXiv:0903.0652. Bibcode:2009ApJS..182...97W. doi:10.1088/0067-0049/182/1/97. S2CID 7422668.

External links[edit]