|
Pi Hydrae (π Hya, π Hydrae) is a star in the constellation Hydra with an apparent visual magnitude of 3.3,〔 making it visible to the naked eye. Parallax measurements put this star at a distance of about from the Earth. The spectrum of this star shows it to have a stellar classification of K1 III-IV,〔 with the luminosity class of 'III-IV' suggesting it is in an evolutionary transition stage somewhere between a subgiant and a giant star. It has a low projected rotational velocity of 2.25 km s−1.〔 Pi Hydrae is radiating energy from its outer envelope with an effective temperature of 4,670 K,〔 giving it the orange hue of a K-type star.〔 Pi Hydrae is a type of giant known as a cyanogen-weak star, which means that its spectrum displays weak absorption lines of CN− relative to the metallicity. (The last is a term astronomers use when describing the abundance of elements other than hydrogen and helium.) Otherwise, it appears to be a normal star of its evolutionary class, having undergone first dredge-up of nuclear fusion by-products onto its surface layers.〔 The measured angular diameter of this star, after correction for limb darkening, is .〔 At its estimated distance, this yields a physical size of about 12–13 times the radius of the Sun.〔 It has an estimated mass of 2.45 times the mass of the Sun.〔 == References == } \\ & \approx 25.1\cdot R_ \end〕 }} 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pi Hydrae」の詳細全文を読む スポンサード リンク
|