51_Ophiuchi
51 Ophiuchi
Star in the constellation Ophiuchus
51 Ophiuchi is a single[8] star located approximately 410[1] light years away from the Sun in the equatorial constellation of Ophiuchus, northwest of the center of the Milky Way. It is visible to the naked eye as a faint, blue-white point of light with an apparent visual magnitude of 4.81.[2] The star is moving closer to the Earth with a heliocentric radial velocity of –12 km/s.[4]
This object is notable for being "a rare, nearby example of a young planetary system just entering the last phase of planet formation".[10] There is uncertainty about the stellar classification of this star. It has the nominal classification of B9.5IIIe, a B-type giant star with emission lines. However, it has also been classified as an A0 II-IIIe star and as a Herbig Ae/Be star.[11] 51 Ophiuchi is about 300,000[8] years old with 3.3 times the mass of the Sun and a polar radius 5.7 times the Sun's radius.[5] It is radiating three[6] times the Sun's luminosity from its photosphere at an effective temperature of 9,772 K.[6] The star is spinning rapidly with a projected rotational velocity of 267 km/s,[7] close to the critical rotation rate.[5]