ABSTRACT
Ultrashort-period (USP) exoplanets have orbital periods shorter than 1 day. Precise masses and radii of USP exoplanets could provide constraints on their unknown formation and evolution processes. We report the detection and characterization of the USP planet GJ 367b using high-precision photometry and radial velocity observations. GJ 367b orbits a bright (V-band magnitude of 10.2), nearby, and red (M-type) dwarf star every 7.7 hours. GJ 367b has a radius of 0.718 ± 0.054 Earth-radii and a mass of 0.546 ± 0.078 Earth-masses, making it a sub-Earth planet. The corresponding bulk density is 8.106 ± 2.165 grams per cubic centimeterclose to that of iron. An interior structure model predicts that the planet has an iron core radius fraction of 86 ± 5%, similar to that of Mercury's interior.
ABSTRACT
Hereditary hemochromatosis is caused by a potentially lethal recessive gene (HFE, C282Y allele) that increases iron absorption and reaches polymorphic levels in northern European populations. Because persons carrying the allele absorb iron more readily than do noncarriers, it has often been suggested that HFE is an adaptation to anemia. We hypothesize positive selection for HFE began during or after the European Neolithic with the adoption of an iron-deficient high-grain and dairying diet and consequent anemia, a finding confirmed in Neolithic and later European skeletons. HFE frequency compared with rate of lactase persistence in Eurasia yields a positive linear correlation coefficient of 0.86. We suggest this is just one of many mutations that became common after the adoption of agriculture.
