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

Star

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. The age of the star is estimated at 3.7 billion years, with metallicity 1.35 times that of the Sun based on its abundance of iron.

Planetary system

In April 2001, two giant planets were announced orbiting the star. 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. In 2022, the inclination and true mass of HD 74156 c were measured via astrometry.

Claims of a third planet

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. 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. 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. However, Roman V. Baluev has cast doubt on this discovery, suggesting that the observed variations may be due to annual errors in the data. A subsequent search using the Hobby-Eberly Telescope also failed to confirm the planet, and further data obtained using HIRES instrument strongly contradicts its existence.

See also

• List of extrasolar planets
• HD 37124
• Upsilon Andromedae

References

1. ^ 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. ^ 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. ^ 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

• "Notes for star HD 74156". Extrasolar Planets Encyclopaedia. Archived from the original on July 2, 2007.
• Extrasolar Planet Interactions Archived 2016-05-05 at the Wayback Machine by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona

• Hydra (constellation)
• Henry Draper Catalogue objects
• Hipparcos objects
• G-type main-sequence stars
• Planetary systems with two confirmed planets
• Durchmusterung objects
• 2MASS objects