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Rho Coronae Borealis
Rho Coronae Borealis (ρ CrB, ρ Coronae Borealis) is a Solar twin, yellow dwarf star approximately 57 light-years away in the constellation of Corona Borealis. The star is thought to be similar to the Sun with nearly the same mass, radius, and luminosity. In 1997, an extrasolar planet was announced on the basis of radial velocity measurements. This detection method gives only a minimum mass on the planet. Follow-up studies with the Hipparcos satellite indicate that the companion is actually low-mass star in a nearly face-on orbit.
== Stellar components ==
Rho Coronae Borealis is a Solar twin, yellow dwarf star of the spectral type "G0-2Va". The star is thought to have only 95 percent of the Sun's mass, along with 1.31 times its radius and 1.61 of its luminosity. It may only be 51 to 65 percent as enriched with elements heavier than hydrogen (based on its abundance of iron) and may be somewhat older than the Sun at around six billion years old.
A companion, initially thought to be an extrasolar planet in a 39.6-day orbit was discovered in 1997 by observing the star's radial velocity variations. This detection method only gives a lower limit on the true mass of the companion. In 2001, preliminary ''Hipparcos'' astrometrical satellite data indicated that the orbital inclination of the star's companion was 0.5°, nearly face-on, implying that its mass was as much as 115 times Jupiter's. This was confirmed in 2011 using a new reduction of the astrometric data, with an updated mass value of 169.7 times Jupiter, with a 3σ confidence region 100.1 to 199.6 Jupiter masses.〔 Such a massive body would be a dim red dwarf star, not a planet.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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