HD 27894
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HD 27894 is a single star with a system of orbiting exoplanets, located in the southern constellation of Reticulum. It is too faint to be seen with the naked eye at an apparent visual magnitude of 9.36.<ref name=Anderson_Francis_2012/> This system lies at a distance of 142.5 light years from the Sun, as determined via parallax measurements, and is drifting further away with a radial velocity of 83 km/s.<ref name=Soubiran_et_al_2018/>
The spectrum of HD 27894 presents as a K-type main-sequence star, an orange dwarf,<ref name="Moutou2005"/> with a stellar classification of K2 V.<ref name=houk1979/> This is a quiescent solar-type star that displays no significant magnetic activity in its chromosphere<ref name="Trifonov2017"/> and is spinning slowly with a rotation period of roughly 44 days.<ref name="Moutou2005"/> The abundance of iron in the star is much higher than in the Sun, an indicator that it is metal-rich.<ref name="Moutou2005"/> It has 83% of the mass of the Sun and 79% of the Sun's radius. The star is radiating 33% of the luminosity of the Sun from its photosphere at an effective temperature of 4,923 K.<ref name=Bonfanti_et_al_2016/>
Planetary systemEdit
In 2005, the Geneva Extrasolar Planet Search Team announced the discovery of an extrasolar planet orbiting the star.<ref name="Moutou2005"/> In 2017, the discovery of two additional exoplanets was announced. One is very close to the star like the one discovered earlier, while the other one orbits the star at a much larger distance. It is the first system where such a large gap between orbital distances has been found.<ref name="Trifonov2017"/><ref name=phys.org/> In 2022, the inclination and true mass of HD 27894 d were measured via astrometry. The study only found strong evidence for planets b and d.<ref name="Feng2022"/>
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