HD 74156
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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.<ref name="GaiaDR3"/> 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.<ref name="Meschiari2011"/> The age of the star is estimated at 3.7 billion years,<ref name="Meschiari2011"/> 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.<ref name="eso0114"/><ref name="Naef2004"/> 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.<ref name="Meschiari2011"/> In 2022, the inclination and true mass of HD 74156 c were measured via astrometry.<ref name="Feng2022"/>
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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.<ref name="Raymond2005"/> 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.<ref name="Bean2008"/> 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.<ref name="Barnes2008"/> However, Roman V. Baluev has cast doubt on this discovery, suggesting that the observed variations may be due to annual errors in the data.<ref name="Baluev2009"/> A subsequent search using the Hobby-Eberly Telescope also failed to confirm the planet,<ref name="Wittenmyer2009"/> and further data obtained using HIRES instrument strongly contradicts its existence.<ref name="Meschiari2011"/>
See also
References
External links
- Template:Cite encyclopedia
- Extrasolar Planet Interactions Template:Webarchive by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona